MicroConverter

Multichannel

24-/16-Bit ADCs with Embedded 62 kB

Flash and Single-Cycle MCU

ADuC845/ADuC847/ADuC848

Rev. A

Information furnished by Analog Devices is believed to be accurate and reliable.
However, no responsibility is assumed by Analog Devices for its use, nor for any
infringements of patents or other rights of third parties that may result from its use.
Specifications subject to change without notice. No license is granted by implication
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One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700

www.analog.com

Fax: 781.326.8703

FEATURES

High resolution - ADCs
Two independent 24-bit ADCs on the ADuC845

Single 24-bit ADC on the ADuC847 and
single 16-bit ADC on the ADuC848
Up to 10 ADC input channels on all parts
24-bit no missing codes
22-bit rms (19.5 bit p-p) effective resolution
Offset drift 10 nV/°C, gain drift 0.5 ppm/°C chop enabled

Memory

62-kbyte on-chip Flash/EE program memory
4-kbyte on-chip Flash/EE data memory
Flash/EE, 100 year retention, 100 kcycle endurance
3 levels of Flash/EE program memory security
In-circuit serial download (no external hardware)
High speed user download (5 seconds)
2304 bytes on-chip data RAM

8051-based core

8051-compatible instruction set
High performance single-cycle core
32 kHz external crystal
On-chip programmable PLL (12.58 MHz max)
3 Ч 16-bit timer/counter
24 programmable I/O lines, plus 8 analog or
digital input lines
11 interrupt sources, two priority levels
Dual data pointer, extended 11-bit stack pointer

On-chip peripherals

Internal power-on reset circuit
12-bit voltage output DAC
Dual 16-bit - DACs
On-chip temperature sensor (ADuC845 only)
Dual excitation current sources (200 µA)
Time interval counter (wake-up/RTC timer)
UART, SPI®, and I

C® serial I/O

High speed dedicated baud rate generator (incl 115,200)
Watchdog timer (WDT)
Power supply monitor (PSM)

Power

Normal: 4.8 mA max @ 3.6 V (core CLK = 1.57 MHz)
Power-down: 20 µA max with wake-up timer running
Specified for 3 V and 5 V operation
Package and temperature range:

52-lead MQFP (14 mm Ч 14 mm), -40°C to +125°C
56-lead CSP (8 mm Ч 8 mm), -40°C to +85°C

APPLICATIONS

Multichannel sensor monitoring
Industrial/environmental instrumentation
Weigh scales, pressure sensors, temperature monitoring
Portable instrumentation, battery-powered systems
Data logging, precision system monitoring

FUNCTIONAL BLOCK DIAGRAM

62 kBYTES FLASH/EE PROGRAM MEMORY

4 kBYTES FLASH/EE DATA MEMORY

2304 BYTES USER RAM

Ч 16 BIT TIMERS

BAUD RATE TIMER

Ч PARALLEL

PORTS

SINGLE-CYCLE 8061 BASED MCU

ADuC845

TEMP

SENSOR

CURRENT

SOURCE

AIN0

AIN9

AINCOM

RESET

DGND

WAKE-UP/

RTC TIMER

IEXC1
IEXC2

PWM0

PGA

BUF

MUX

AUXILIARY

24-BIT

- ADC

PRIMARY

24-BIT

- ADC

DAC

BUF

PWM1

12-BIT

DAC

DUAL 16-BIT

- DAC

DUAL 16-BIT

PWM

POWER SUPPLY MON

WATCHDOG TIMER

UART, SPI, AND I

SERIAL I/O

MUX

04741-

001

XTAL2

XTAL1

OSC

AVCO

AGND

PLL AND PRG

CLOCK DIV

POR

REFIN+

REFIN

REFIN2

REFIN2+

EXTERNAL

REF

DETECT

INTERNAL

BAND GAP

REF

Figure 1. ADuC845 Functional Block Diagram

ADuC845/ADuC847/ADuC848

Rev. A | Page 2 of 108

TABLE OF CONTENTS

Specifications..................................................................................... 4

Abosolute Maximum Ratings ....................................................... 10

ESD Caution................................................................................ 10

Pin Configuration and Function Descriptions........................... 11

General Description ....................................................................... 15

8052 Instruction Set ................................................................... 18

Timer Operation......................................................................... 18

ALE............................................................................................... 18

External Memory Access ........................................................... 18

Complete SFR Map .................................................................... 19

Functional Description .................................................................. 20

8051 Instruction Set ................................................................... 20

Memory Organization ............................................................... 22

Special Function Registers (SFRs)............................................ 24

ADC Circuit Information.......................................................... 26

Auxiliary ADC (ADuC845 Only) ............................................ 32

Reference Inputs ......................................................................... 32

Burnout Current Sources .......................................................... 32

Reference Detect Circuit ........................................................... 33

Sinc Filter Register (SF) ............................................................. 33

- Modulator ............................................................................ 33

Digital Filter ................................................................................ 33

ADC Chopping........................................................................... 34

Calibration................................................................................... 34

Programmable Gain Amplifier ................................................. 35

Bipolar/Unipolar Configuration .............................................. 35

Data Output Coding .................................................................. 36

Excitation Currents .................................................................... 36

ADC Power-On .......................................................................... 36

Typical Performance Characteristics ........................................... 37

Functional Description .................................................................. 39

ADC SFR Interface..................................................................... 39

ADCSTAT (ADC Status Register) ........................................... 40

ADCMODE (ADC Mode Register)......................................... 41

ADC0CON1 (Primary ADC Control Register)..................... 43

ADC0CON2 (Primary ADC Channel Select Register) ........ 44

SF (ADC Sinc Filter Control Register) .................................... 46

ICON (Excitation Current Sources Control Register) .......... 47

Nonvolatile Flash/EE Memory Overview ............................... 48

Flash/EE Program Memory ...................................................... 49

User Download Mode (ULOAD)............................................. 50

Using Flash/EE Data Memory.................................................. 51

Flash/EE Memory Timing ........................................................ 52

DAC Circuit Information.......................................................... 53

Pulse-Width Modulator (PWM).............................................. 55

On-Chip PLL (PLLCON).......................................................... 60

C Serial Interface ..................................................................... 61

SPI Serial Interface ..................................................................... 64

Using the SPI Interface .............................................................. 66

Dual Data Pointers ..................................................................... 67

Power Supply Monitor ............................................................... 68

Watchdog Timer......................................................................... 69

Time Interval Counter (TIC).................................................... 70

8052 Compatible On-Chip Peripherals................................... 73

Timers/Counters ........................................................................ 75

UART Serial Interface................................................................ 80

Interrupt System ......................................................................... 85

Interrupt Priority........................................................................ 86

Interrupt Vectors ........................................................................ 86

Hardware Design Considerations ................................................ 87

External Memory Interface....................................................... 87

Power Supplies............................................................................ 87

ADuC845/ADuC847/ADuC848

Rev. A | Page 3 of 108

Power-On Reset Operation........................................................88

Power Consumption ...................................................................88

Power-Saving Modes ..................................................................88

Grounding and Board Layout Recommendations .................89

Other Hardware Considerations...............................................90

QuickStart Development System ..................................................94

QuickStart-PLUS Development System ..................................94

Timing Specifications .....................................................................95

Outline Dimensions......................................................................104

Ordering Guide .........................................................................105

REVISION HISTORY

6/04--Changed from Rev. 0 to Rev. A

Changes to Figure 5.........................................................................17
Changes to Figure 6.........................................................................18
Changes to Figure 7.........................................................................19
Changes to Table 5 ..........................................................................24
Changes to Table 24 ........................................................................41
Changes to Table 25 ........................................................................43
Changes to Table 26 ........................................................................44
Changes to Table 27 ........................................................................45
Changes to User Download Mode Section ..................................50
Added Figure 51 and Renumbered Subsequent Figures............50
Edits to the DACH/DACL Data Registers Section .....................53
Changes to Table 34 ........................................................................56
Added SPIDAT: SPI Data Register Section..................................65
Changes to Table 42 ........................................................................67
Changes to Table 43 ........................................................................68
Changes to Table 44 ........................................................................69
Changes to Table 45 ........................................................................71
Changes to Table 50 ........................................................................75
Changes to Timer/Counter 0 and 1 Data Registers Section......76
Changes to Table 54 ........................................................................80
Added the SBUF--UART Serial Port Data Register Section.....80
Addition to the Timer 3 Generated Baud Rates Section............83
Added Table 57 and Renumbered Subsequent Tables................84
Changes to Table 61 ........................................................................86

4/04--Revision 0: Initial Version

ADuC845/ADuC847/ADuC848

Rev. A | Page 4 of 108

SPECIFICATIONS

= 2.7 V to 3.6 V or 4.75 V to 5.25 V, DV

= 2.7 V to 3.6 V or 4.75 V to 5.25 V, REFIN(+) = 2.5 V, REFIN() = AGND; AGND =

DGND = 0 V; XTAL1/XTAL2 = 32.768 kHz crystal; all specifications T

MIN

to T

MAX

, unless otherwise noted. Input buffer on for primary

ADC, unless otherwise noted. Core speed = 1.57 MHz (default CD = 3), unless otherwise noted.

Table 1.

Parameter Min

Typ

Max

Unit

Conditions

PRIMARY ADC

Conversion Rate

5.4

105

Chop on (ADCMODE.3 = 0)

16.06

1365

Chop off (ADCMODE.3 = 1)

No Missing Codes

Bits

26.7 Hz update rate with chop enabled

Bits

80.3 Hz update rate with chop disabled

Resolution (ADuC845/ADuC847)

See Table 11 and Table 15

Resolution (ADuC848)

See Table 13 and Table 17

Output Noise (ADuC845/ADuC847)

See Table 10 and Table 14

µV (rms)

Output noise varies with selected update rates,

gain range, and chop status.

Output Noise (ADuC848)

See Table 12 and Table 16

µV (rms)

Output noise varies with selected update rates,

gain range and chop status.

Integral Nonlinearity

±15

ppm of FSR

1 LSB

Offset Error

±3

µV

Chop on

Chop off, offset error is in the order of the noise

for the programmed gain and update rate
following a calibration.

Offset Error Drift vs. Temperature

±10

nV/°C

Chop on (ADCMODE.3 = 0)

±200

nV/°C

Chop off (ADCMODE.3 = 1)

Full-Scale Error

ADuC845/ADuC847

±10

µV

±20 mV to ±2.56 V

ADuC848

±10

µV

±20 mV to ±640 mV

±0.5

LSB

±1.28 V to ±2.56 V

Gain Error Drift vs. Temperature

±0.5

ppm/°C

Power Supply Rejection

AIN = 1 V, ±2.56 V, chop enabled

113

AIN = 7.8 mV, ±20 mV, chop enabled

AIN = 1 V, ±2.56 V, chop disabled

PRIMARY ADC ANALOG INPUTS

Differential Input Voltage Ranges

5, 6

Gain = 1 to 128

Bipolar Mode (ADC0CON1.5 = 0)

±1.024 Ч
V

REF

/GAIN

REF

= REFIN(+) - REFIN(-) or

REFIN2(+) - REFIN2(-) (or Int 1.25 V

REF

)

Unipolar Mode (ADC0CON1.5 = 1)

0 1.024 Ч
V

REF

/GAIN

REF

= REFIN(+) - REFIN(-) or

REFIN2(+) - REFIN2(-) (or Int 1.25 V

REF

)

ADC Range Matching

±2

µV

AIN = 18 mV, chop enabled

Common-Mode Rejection DC

Chop enabled, chop disabled

On AIN

AIN = 7.8 mV, range = ±20 mV

113

AIN = 1 V, range = ±2.56 V

Common-Mode Rejection
50 Hz/60 Hz

50 Hz/60 Hz ± 1 Hz, 16.6 Hz and 50 Hz update
rate, chop enabled, REJ60 enabled

On AIN

AIN = 7.8 mV, range = ±20 mV

AIN = 1 V, range = ±2.56 V

Footnotes at end of table.

ADuC845/ADuC847/ADuC848

Rev. A | Page 5 of 108

Parameter Min

Typ

Max

Unit

Conditions

Normal Mode Rejection 50 Hz/60

On AIN

50 Hz/60 Hz ± 1 Hz, 16.6 Hz Fadc, SF = 52H,
chop on, REJ60 on

100

50 Hz ± 1 Hz, 16.6 Hz Fadc, SF = 52H, chop on

50 Hz/60 Hz ± 1 Hz, 50 Hz Fadc, SF = 52H,
chop off, REJ60 on

100

50 Hz ± 1 Hz, 50 Hz Fadc, SF = 52H, chop off

Analog Input Current

±1

MAX

= 85°C, buffer on

±5

MAX

= 125°C, buffer on

Analog Input Current Drift

±5

pA/°C

MAX

= 85°C, buffer on

±15

pA/°C

MAX

= 125°C, buffer on

Average Input Current

±125

nA/V

±2.56 V range, buffer bypassed

Average Input Current Drift

±2

pA/V/°C

Buffer bypassed

Absolute AIN Voltage Limits

GND

0.1

AIN1...AIN10 and AINCOM with buffer enabled

Absolute AIN Voltage Limits

GND

0.03

AIN1...AIN10 and AINCOM with buffer bypassed

EXTERNAL REFERENCE INPUTS

REFIN(+) to REFIN() Voltage

2.5

REFIN refers to both REFIN and REFIN2

REFIN(+) to REFIN() Range

REFIN refers to both REFIN and REFIN2

Average Reference Input Current

±1

µA/V

Both ADCs enabled

Average Reference Input Current
Drift

±0.1

nA/V/°C

NOXREF Trigger Voltage

0.3

0.65

NOXREF (ADCSTAT.4) bit active if V

REF

> 0.3 V, and

inactive if V

REF

> 0.65 V

Common-Mode Rejection

DC Rejection

125

AIN = 1 V, range = ±2.56 V

50 Hz/60 Hz Rejection

dB 50 Hz/60 Hz ± 1 Hz, AIN = 1 V,

range = ±2.56 V, SF = 82

Normal Mode Rejection 50 Hz/60 Hz

dB 50 Hz/60 Hz ±1 Hz, AIN = 1 V, range = ±2.56 V,

SF = 52H, chop on, REJ60 on

100

50 Hz ± 1 Hz, AIN = 1 V, range = ±2.56 V,
SF = 52H, chop on

50 Hz/60 Hz ± 1 Hz, AIN = 1 V, range = ±2.56 V,
SF = 52H, chop off, REJ60 on

100

50 Hz ± 1 Hz, AIN = 1 V, range = ±2.56 V,
SF = 52H, chop off

AUXILIARY ADC (ADuC845 Only)

Conversion Rate

5.4

105

Chop on

16.06

1365

Chop

off

No Missing Codes

Bits

26.7 Hz update rate, chop enabled

Bits

80.3 Hz update rate, chop disabled

Resolution

See Table 19 and Table 21

Output Noise

See Table 18 and Table 20

Output noise varies with selected update rates.

Integral Nonlinearity

±15

ppm of FSR

1 LSB

Offset Error

±3

µV

Chop

±0.25

LSB

Chop

off

Offset Error Drift

nV/°C

Chop on

200

nV/°C

Chop off

Full-Scale Error

±0.5

LSB

Gain Error Drift

±0.5

ppm/°C

Power Supply Rejection

AIN = 1 V, range = ±2.56 V, chop enabled

AIN = 1 V, range = ±2.56 V, chop disabled

Footnotes at end of table.

ADuC845/ADuC847/ADuC848

Rev. A | Page 6 of 108

Parameter Min

Typ

Max

Unit

Conditions

AUXILIARY ADC ANALOG INPUTS
(ADuC845 Only)

Differential Input Voltage Ranges

5, 6

Bipolar Mode (ADC1CON.5 = 0)

±V

REF

REFIN = REFIN(+) - REFIN(-) (or Int 1.25 V

REF

)

Unipolar Mode (ADC1CON.5 = 1)

0 V

REF

REFIN = REFIN(+) - REFIN(-) (or Int 1.25 V

REF

)

Average Analog Input Current

125

nA/V

Analog Input Current Drift

±2

pA/V/°C

Absolute AIN/AINCOM Voltage
Limits

2, 7

GND

0.03

Normal Mode Rejection 50 Hz/60 Hz

On AIN and REFIN

50 Hz/60 Hz ± 1 Hz, 16.6 Hz Fadc, SF = 52H,
chop on, REJ60 on

100

50 Hz ± 1 Hz, 16.6 Hz Fadc, SF = 52H, chop on

50 Hz/60 Hz ± 1 Hz, 50 Hz Fadc, SF = 52H,
chop off, REJ60 on

100

50 Hz ± 1 Hz, 50 Hz Fadc, SF = 52H, chop off

ADC SYSTEM CALIBRATION

Full-Scale Calibration Limit

+1.05 Ч FS

Zero-Scale Calibration Limit

-1.05 Ч FS

Input Span

0.8 Ч FS

2.1 Ч FS

DAC

Voltage Range

0 V

REF

DACCON.2 = 0

0 AV

DACCON.2 = 1

Resistive Load

From DAC output to AGND

Capactive Load

100

From DAC output to AGND

Output Impedance

0.5

SINK

µA

DC Specifications

Resolution 12

Bits

Relative Accuracy

±3

LSB

Differential Non Linearity

-1

LSB

Guaranteed 12-bit monotonic

Offset Error

±50

Gain Error

±1

range

±1

REF

range

AC Specifications

2, 8

Voltage Output Settling Time

µs

Settling time to 1 LSB of final value

Digital-to-Analog Glitch Energy

nVs

1 LSB change at major carry

INTERNAL REFERENCE

ADC Reference

Chop enabled

Reference Voltage

1.25 - 1%

1.25

1.25 + 1%

Initial tolerance @ 25°C, V

= 5 V

Power Supply Rejection

Reference Tempco

100

ppm/°C

DAC Reference

Reference Voltage

2.5 1%

2.5

2.5 + 1%

±1% V

Initial tolerance @ 25°C, V

= 5 V

Power Supply Rejection

Reference Tempco

±100

ppm/°C

TEMPERATURE SENSOR
(ADuC845 Only)

Accuracy

±2

°C

Thermal Impedance

°C/W

MQFP package

°C/W

CSP

package

Footnotes at end of table.

ADuC845/ADuC847/ADuC848

Rev. A | Page 7 of 108

Parameter Min

Typ

Max

Unit

Conditions

TRANSDUCER BURNOUT CURRENT
SOURCES

AIN+ Current

-100

AIN+ is the selected positive input (AIN4 or AIN6

only) to the primary ADC

AIN- Current

100

AIN- is the selected negative input (AIN5 or AIN7

only) to the primary ADC

Initial Tolerance at 25°C

±10

Drift

0.03

%/°C

EXCITATION CURRENT SOURCES

Output Current

200

µA

Available from each current source

Initial Tolerance at 25°C

±10

Drift

200

ppm/°C

Initial Current Matching at 25°C

±1

Matching between both current sources

Drift Matching

ppm/°C

Line Regulation (AV

)

µA/V

= 5 V ± 5%

Load Regulation

0.1

µA/V

Output Compliance

AGND

- 0.6

POWER SUPPLY MONITOR (PSM)

Trip Point Selection Range

2.63

4.63

Four trip points selectable in this range

Trip Point Accuracy

±3.0

MAX

= 85°C

±4.0

MAX

= 125°C

Trip Point Selection Range

2.63

4.63

Four trip points selectable in this range

Trip Point Accuracy

±3.0

MAX

= 85°C

±4.0

MAX

= 125°C

CRYSTAL OSCILLATOR
(XTAL1 AND XTAL2)

Logic Inputs, XTAL1 Only

INL

, Input Low Voltage

0.8

= 5 V

0.4

= 3 V

INH

, Input Low Voltage

3.5

= 5 V

2.5

= 3 V

XTAL1 Input Capacitance

XTAL2 Output Capacitance

LOGIC INPUTS

All inputs except SCLOCK, RESET,
and XTAL1

INL

, Input Low Voltage

0.8

= 5 V

0.4

= 3 V

INH

, Input Low Voltage

2.0

SCLOCK and RESET Only
(Schmidt Triggered Inputs)

T+

1.3

3.0

= 5 V

0.95

2.5

= 3 V

T-

0.8

1.4

= 5 V

0.4

1.1

= 3 V

T+

- V

T-

0.3

0.85

= 5 V or 3 V

Input Currents

Port 0, P1.0 to P1.7, EA

±10

µA V

= 0 V or V

RESET

±10

µA

= 0 V, DV

= 5 V

105

µA

= DV

, DV

= 5 V, internal pull-down

Port 2, Port 3

±10

µA

= DV

, DV

= 5 V

-180

-660

µA

= 2 V, DV

= 5 V

-20

-75

µA

= 0.45 V, DV

= 5 V

Input Capacitance

All digital inputs

ADuC845/ADuC847/ADuC848

Rev. A | Page 8 of 108

Parameter Min

Typ

Max

Unit

Conditions

LOGIC OUTPUTS
(All Digital Outputs except XTAL2)

, Output High Voltage

2.4

V DV

= 5 V, I

SOURCE

= 80 µA

2.4

= 3 V, I

SOURCE

= 20 µA

, Output Low Voltage

0.4

SINK

= 8 mA, SCLOCK, SDATA

0.4

SINK

= 1.6 mA on P0, P1, P2

Floating State Leakage Current

±10 µA

Floating State Output Capacitance

START-UP TIME

At Power-On

600

After Ext RESET in Normal Mode

After WDT RESET in Normal Mode

Controlled via WDCON SFR

From Power-Down Mode

Oscillator Running

PLLCON.7 = 0

Wake-Up with INT0 Interrupt

µs

Wake-Up with SPI Interrupt

µs

Wake-Up with TIC Interrupt

µs

Oscillator Powered Down

PLLCON.7 = 1

Wake-Up with INT0 Interrupt

µs

Wake-Up with SPI Interrupt

µs

FLASH/EE MEMORY RELIABILITY
CHARACTERISTICS

Endurance

100,000

Cycles

Data Retention

100

Years

POWER REQUIREMENTS

Power Supply Voltages

3 V Nominal

2.7

3.6

5 V Nominal

4.75

5.25

3 V Nominal

2.7

3.6

5 V Nominal

4.75

5.25

5 V Power Consumption

4.75 V < DV

< 5.25 V, AV

= 5.25 V

Normal Mode

11, 12

Current

Core clock = 1.57 MHz

Core clock = 12.58 MHz

Current

180

µA

Power-Down Mode

11, 12

Current

µA

MAX

= 85°C; OSC on; TIC on

µA

MAX

= 125°C; OSC on; TIC on

µA

MAX

= 85°C; OSC off

µA

MAX

= 125°C; OSC off

Current

µA

MAX

= 85°C; OSC on or off

µA

MAX

= 125°C; OSC on or off

Typical Additional Peripheral
Currents (AI

and DI

)

5 V V

, CD = 3

Primary ADC

Auxiliary ADC (ADuC845 Only)

0.5

Power Supply Monitor

µA

DAC

µA

DACH/L = 000H

Dual Excitation Current Sources

200

µA

200 µA each. Can be combined to give 400 µA on

a single output.

ALE Off

-20

µA

PCON.4 = 1 (see Table 6)

WDT

µA

Footnotes at end of table.

ADuC845/ADuC847/ADuC848

Rev. A | Page 9 of 108

Parameter Min

Typ

Max

Unit

Conditions

PWM

-Fxtal

µA

-Fvco

0.5

TIC

µA

3 V Power Consumption

2.7 V < DV

< 3.6 V, AV

= 3.6 V

Normal Mode

11, 12

Current

4.8

Core clock = 1.57 MHz

Core clock = 6.29 MHz (CD = 1)

Current

180

µA

ADC not enabled

Power-Down Mode

11, 12

Current

µA

MAX

= 85°C; OSC on; TIC on

µA

MAX

= 125°C; OSC on; TIC on

µA

max

= 85°C; OSC off

µA

MAX

= 125°C; OSC off

Current

µA

MAX

= 85°C; OSC on or off

µA

MAX

= 125°C; OSC on or off

Temperature range is for ADuC845BS; for the ADuC847BS and ADuC848BS (MQFP package), the range is 40°C to +125°C.

Temperature range for ADuC845BCP, ADuC847BCP, and ADuC848BCP (CSP package) is 40°C to +85°C.

These numbers are not production tested but are guaranteed by design and/or characterization data on production release.

System zero-scale calibration can remove this error.

Gain error drift is a span drift. To calculate full-scale error drift, add the offset error drift to the gain error drift times the full-scale input.

In general terms, the bipolar input voltage range to the primary ADC is given by the ADC range = ±(V

REF

)/1.25, where:

REF

= REFIN(+) to REFIN() voltage and V

REF

= 1.25 V when internal ADC V

REF

is selected. RN = decimal equivalent of RN2, RN1, RN0. For example, if V

REF

= 2.5 V and RN2,

RN1, RN0 = 1, 1, 0, respectively, then the ADC range = ±1.28 V. In unipolar mode, the effective range is 0 V to 1.28 V in this example.

1.25 V is used as the reference voltage to the ADC when internal V

REF

is selected via XREF0/XREF1 or AXREF bits in ADC0CON2 and ADC1CON, respectively.

(AXREF is available only on the ADuC845.)

In bipolar mode, the auxiliary ADC can be driven only to a minimum of AGND 30 mV as indicated by the auxiliary ADC absolute AIN voltage limits. The bipolar range is

still V

REF

to +V

REF

DAC linearity and ac specifications are calculated using a reduced code range of 48 to 4095, 0 V to V

REF

, reduced code range of 100 to 3950, 0 V to VDD.

Endurance is qualified to 100 kcycle per JEDEC Std. 22 method A117 and measured at 40°C, +25°C, +85°C, and +125°C. Typical endurance at 25°C is 700 kcycles.

Retention lifetime equivalent at junction temperature (T

) = 55°C per JEDEC Std. 22, Method A117. Retention lifetime based on an activation energy of 0.6 eV derates

with junction temperature.

Power supply current consumption is measured in normal mode following the power-on sequence, and in power-down modes under the following conditions:

Normal mode: reset = 0.4 V, digital I/O pins = open circuit, Core Clk changed via CD bits in PLLCON, core executing internal software loop.
Power-down mode: reset = 0.4 V, all P0 pins and P1.2 to P1.7 pins = 0.4 V. All other digital I/O pins are open circuit, core Clk changed via CD bits in PLLCON, PCON.1 = 1,
core execution suspended in power-down mode, OSC turned on or off via OSC_PD bit (PLLCON.7) in PLLCON SFR.

power supply current increases typically by 3 mA (3 V operation) and 10 mA (5 V operation) during a Flash/EE memory program or erase cycle.

General Notes about Specifications

· DAC gain error is a measure of the span error of the DAC.

· The ADuC845BCP, ADuC847BCP, and ADuC848BCP (CSP package) have been qualified and tested with the base of the CSP

package floating. The base of the CSP package should be soldered to the board, but left floating electrically, to ensure good
mechanical stability.

· Flash/EE memory reliability characteristics apply to both the Flash/EE program memory and Flash/EE data memory.

ADuC845/ADuC847/ADuC848

Rev. A | Page 10 of 108

ABOSOLUTE MAXIMUM RATINGS

= 25°C, unless otherwise noted.

Table 2.

Parameter Rating

to AGND

0.3 V to +7 V

to DGND

0.3 V to +7 V

to DGND

0.3 V to +7 V

to DGND

0.3 V to +7 V

AGND to DGND

0.3 V to +0.3 V

to DV

2 V to +5 V

Analog Input Voltage to AGND

0.3 V to AV

+ 0.3 V

Reference Input Voltage to AGND

0.3 V to AV

+ 0.3 V

AIN/REFIN Current (Indefinite)

30 mA

Digital Input Voltage to DGND

0.3 V to DV

+ 0.3 V

Digital Output Voltage to DGND

0.3 V to DV

+ 0.3 V

Operating Temperature Range

40°C to +125°C

Storage Temperature Range

65°C to +150°C

Junction Temperature

150°C

Thermal Impedance (MQFP)

90°C/W

Thermal Impedance (LFCSP)

52°C/W

Lead Temperature, Soldering

Vapor Phase (60 sec)

215°C

Infrared (15 sec)

220°C

Stresses above those listed under Absolute Maximum Ratings
may cause permanent damage to the device. This is a stress
rating only; functional operation of the device at these or any
other conditions above those listed in the operational sections
of this specification is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect
device reliability.

________________________

AGND and DGND are shorted internally on the ADuC845, ADuC847, and ADuC848.

Applies to the P1.0 to P1.7 pins operating in analog or digital input modes.

ESD CAUTION

ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on
the human body and test equipment and can discharge without detection. Although this product features
proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy
electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance
degradation or loss of functionality.

ADuC845/ADuC847/ADuC848

Rev. A | Page 11 of 108

PIN CONFIGURATION AND FUNCTION DESCRIPTIONS

52 51 50 49 48

43 42 41 40

47 46 45 44

14 15 16 17 18 19 20 21 22 23 24 25 26

3
4

PIN 1

IDENTIFIER

TOP VIEW

(Not to Scale)

P0.7/AD

P0.6/AD

P0.5/AD

P0.4/AD

DGND

P0.3/AD

P0.2/AD

P0.1/AD1

P0.0/AD

ALE

PSEN

DAC

RESET

P3.0/RxD

P3.1/TxD

P3.2/INT0

P3.3/INT1

P3.4/T0

P3.5/T1

P3.6/WR

P3.7/RD

SCLOCK (I

P1.0/AIN1
P1.1/AIN2

P1.2/AIN3/REFIN2+
P1.3/AIN4/REFIN2

AGND

REFIN
REFIN+

P1.4/AIN5
P1.5/AIN6

P1.6/AIN7/IEXC1
P1.7/AIN8/IEXC2

AINCOM/DAC

P2.7/PWMCLK
P2.6/PWM1

P2.5/PWM0
P2.4/T2EX
DGND

XTAL2
XTAL1

P2.3/SS/T2
P2.2/MISO

P2.1/MOSI
P2.0/SCLOCK (SPI)

SDATA

DGND

04741-

0
-
0
02

ADuC845/ADuC847/ADuC848

Figure 2. 52-Lead MQFP Pin Configuration

P1.1/AIN2

P1.2/AIN3/REFIN2+
P1.3/AIN4/REFIN2

AGND

REFIN
REFIN+

P1.4/AIN5

P1.5/AIN6

P1.6/AIN7/IEXC1
P1.7/AIN8/IEXC2

AINCOM/DAC

DAC

AIN9

AIN10

RESET

/Rx

x
D

/INT

DGND

/WR

/RD

SCLK(

P2.7/PWMCLK
P2.6/PWM1
P2.5/PWM0

P2.4/T2EX
DGND

DGND
DV

XTAL1
P2.3/SS/T2
P2.2/MISO
P2.1/MOSI
P2.0/SCLOCK (SPI)
SDATA

/AIN1

/AD7

/AD6

/AD5

/AD4

DGND

/AD3

/AD2

/AD1

/AD0

ALE

PSEN

1
2
3
4
5
6
7
8
9

10
11

42
41
40
39
38
37
36
35
34
33
32
31
30
29

PIN 1

IDENTIFIER

XTAL2

TOP VIEW

(Not to Scale)

04741-0-003

ADuC845/ADuC847/ADuC848

Figure 3. 56-Lead CSP Pin Configuration

Table 3. Pin Function Descriptions

Pin No:
52-MQFP

Pin No:
56-CSP

Mnemonic

Type

Description

P1.0/AIN1

By power-on default, P1.0/AIN1 is configured as the AIN1 analog input.
AIN1 can be used as a pseudo differential input when used with AINCOM or as
the positive input of a fully differential pair when used with AIN2.
P1.0 has no digital output driver. It can function as a digital input for which 0
must be written to the port bit. As a digital input, this pin must be driven high or
low externally.

P1.1/AIN2

On power-on default, P1.1/AIN2 is configured as the AIN2 analog input.
AIN2 can be used as a pseudo differential input when used with AINCOM or as
the negative input of a fully differential pair when used with AIN1.
P1.1 has no digital output driver. It can function as a digital input for which 0
must be written to the port bit. As a digital input, this pin must be driven high or
low externally.

P1.2/AIN3/REFIN2+

On power-on default, P1.2/AIN3 is configured as the AIN3 analog input.
AIN3 can be used as a pseudo differential input when used with AINCOM or as
the positive input of a fully differential pair when used with AIN4.
P1.2 has no digital output driver. It can function as a digital input for which 0
must be written to the port bit. As a digital input, this pin must be driven high or
low externally. This pin also functions as a second external differential reference
input, positive terminal.

P1.3/AIN4/REFIN2-

On power-on default, P1.3/AIN4 is configured as the AIN4 analog input.
AIN4 can be used as a pseudo differential input when used with AINCOM or as
the negative input of a fully differential pair when used with AIN3.
P1.3 has no digital output driver. It can function as a digital input for which 0
must be written to the port bit. As a digital input, this pin must be driven high or
low externally. This pin also functions as a second external differential reference
input, negative terminal.

5 4

Analog

Supply

Voltage.

6 5

AGND

Analog

Ground.

---

AGND

A second analog ground is provided with the CSP version only.

Footnotes at end of table.

ADuC845/ADuC847/ADuC848

Rev. A | Page 12 of 108

Pin No:
52-MQFP

Pin No:
56-CSP

Mnemonic

Type

Description

7 7

REFIN-

External

Differential

Reference Input, Negative Terminal.

8 8

REFIN+

External

Differential

Reference Input, Positive Terminal.

P1.4/AIN5

On power-on default, P1.4/AIN5 is configured as the AIN5 analog input.
AIN5 can be used as a pseudo differential input when used with AINCOM or as
the positive input of a fully differential pair when used with AIN6.
P1.0 has no digital output driver. It can function as a digital input for which 0
must be written to the port bit. As a digital input, this pin must be driven high or
low externally.

P1.5/AIN6

On power-on default, P1.5/AIN6 is configured as the AIN6 analog input.
AIN6 can be used as a pseudo differential input when used with AINCOM or as
the negative input of a fully differential pair when used with AIN5.
P1.1 has no digital output driver. It can function as a digital input for which 0
must be written to the port bit. As a digital input, this pin must be driven high or
low externally.

P1.6/AIN7/IEXC1

I/O

On power-on default, P1.6/AIN7 is configured as the AIN7 analog input.
AIN7 can be used as a pseudo differential input when used with AINCOM or as
the positive input of a fully differential pair when used with AIN8. One or both
current sources can also be configured at this pin.
P1.6 has no digital output driver. It can, however, function as a digital input for
which 0 must be written to the port bit. As a digital input, this pin must be
driven high or low externally.

P1.7/AIN8/IEXC2

I/O

On power-on default, P1.7/AIN8 is configured as the AIN8 analog input.
AIN8 can be used as a pseudo differential input when used with AINCOM or as
the negative input of a fully differential pair when used with AIN7. One or both
current sources can also be configured at this pin.
P1.7 has no digital output driver. It can, however, function as a digital input for
which 0 must be written to the port bit. As a digital input, this pin must be
driven high or low externally.

13 13

AINCOM/DAC I/O

All analog inputs can be referred to this pin, provided that a relevant pseudo
differential input mode is selected. This pin also functions as an alternative pin
out for the DAC.

DAC

The voltage output from the DAC, if enabled, appears at this pin.

---- 15 AIN9

AIN9 can be used as a pseudo differential analog input when used with AINCOM
or as the positive input of a fully differential pair when used with AIN10 (CSP
version only).

---- 16 AIN10

AIN10 can be used as a pseudo differential analog input when used with
AINCOM or as the negative input of a fully differential pair when used with AIN9
(CSP version only).

15 17

RESET

Reset Input. A high level on this pin for 16 core clock cycles while the oscillator is
running resets the device. This pin has an internal weak pull-down and a Schmitt
trigger input stage.

1619
2225

1821
2427

P3.0P3.7

I/O

P3.0 to P3.7 are bidirectional port pins with internal pull-up resistors. Port 3 pins
that have 1s written to them are pulled high by the internal pull-up resistors,
and in that state can be used as inputs. As inputs, Port 3 pins being pulled
externally low source current because of the internal pull-up resistors. When
driving a 0-to-1 output transition, a strong pull-up is active for one core clock
period of the instruction cycle.
Port 3 pins also have the various secondary functions described below.

P3.0/RxD

Receiver Data for UART Serial Port.

P3.1/TxD

Transmitter Data for UART Serial Port.

18 20

P3.2/INT0

External Interrupt 0. This pin can also be used as a gate control input to Timer 0.

19 21

P3.3/INT1

External Interrupt 1. This pin can also be used as a gate control input to Timer 1.

P3.4/T0

Timer/Counter 0 External Input.

P3.5/T1

Timer/Counter 1 External Input.

24 26

P3.6/WR

External Data Memory Write Strobe. This pin latches the data byte from Port 0
into an external data memory.

ADuC845/ADuC847/ADuC848

Rev. A | Page 13 of 108

Pin No:
52-MQFP

Pin No:
56-CSP

Mnemonic

Type

Description

25 27

P3.7/RD

External Data Memory Read Strobe. This pin enables the data from an external
data memory to Port 0.

20, 34, 48

22, 36, 51

Digital

Supply

Voltage.

21, 35, 47

23, 37,
38, 50

DGND S

Digital

Ground.

26 28

SCLK

I/O

Serial Interface Clock for the I

C Interface. As an input, this pin is a Schmitt-

triggered input. A weak internal pull-up is present on this pin unless it is
outputting logic low. This pin can also be controlled in software as a digital
output pin.

27 29

SDATA

I/O

Serial Data Pin for the I

C Interface. As an input, this pin has a weak internal pull-

up present unless it is outputting logic low.

2831,
3639

3033,
3942

P2.0P2.7 I/O

Port 2 is a bidirectional port with internal pull-up resistors. Port 2 pins that have
1s written to them are pulled high by the internal pull-up resistors, and in that
state can be used as inputs. As inputs, Port 2 pins being pulled externally low
source current because of the internal pull-up resistors. Port 2 emits the middle
and high-order address bytes during accesses to the 24-bit external data
memory space.
Port 2 pins also have the various secondary functions described below.

28 30

P2.0/SCLOCK

(SPI)

Serial Interface Clock for the SPI Interface. As an input this pin is a Schmitt-
triggered input. A weak internal pull-up is present on this pin unless it is
outputting logic low.

29 31

P2.1/MOSI

Serial Master Output/Slave Input Data for the SPI Interface. A strong internal
pull-up is present on this pin when the SPI interface outputs a logic high. A
strong internal pull-down is present on this pin when the SPI interface outputs a
logic low.

30 32

P2.2/MISO

Master Input/Slave Output for the SPI Interface. A weak pull-up is present on this
input pin.

31 33

P2.3/SS/T2

Slave Select Input for the SPI Interface. A weak pull-up is present on this pin.
For both package options, this pin can also be used to provide a clock input to
Timer 2. When enabled, Counter 2 is incremented in response to a negative
transition on the T2 input pin.

36 39

P2.4/T2EX

Control Input to Timer 2. When enabled, a negative transition on the T2EX input
pin causes a Timer 2 capture or reload event.

P2.5/PWM0

If the PWM is enabled, the PWM0 output appears at this pin.

P2.6/PWM1

If the PWM is enabled, the PWM1 output appears at this pin.

P2.7/PWMCLK

If the PWM is enabled, an external PWM clock can be provided at this pin.

XTAL1

Input to the Crystal Oscillator Inverter.

33 35

XTAL2

Output from the Crystal Oscillator Inverter. See the Hardware Design
Considerations section for a description.

40 43

External Access Enable, Logic Input. When held high, this input enables the
device to fetch code from internal program memory locations 0000H to F7FFH.
No external program memory access is available on the ADuC845, ADuC847, or
ADuC848. To determine the mode of code execution, the EA pin is sampled at
the end of an external RESET assertion or as part of a device power cycle. EA can
also be used as an external emulation I/O pin, and therefore the voltage level at
this pin must not be changed during normal operation because this might
cause an emulation interrupt that halts code execution.

PSEN

Program Store Enable, Logic Output. This function is not used on the ADuC845,
ADuC847, or ADuC848. This pin remains high during internal program execution.
PSEN can also be used to enable serial download mode when pulled low
through a resistor at the end of an external RESET assertion or as part of a device
power cycle.

42 45

ALE

Address Latch Enable, Logic Output. This output is used to latch the low byte
(and page byte for 24-bit data address space accesses) of the address to external
memory during external data memory access cycles. It can be disabled by
setting the PCON.4 bit in the PCON SFR.

Footnotes at end of table.

ADuC845/ADuC847/ADuC848

Rev. A | Page 15 of 108

GENERAL DESCRIPTION

The ADuC845, ADuC847, and ADuC848 are single-cycle,
12.58 MIPs, 8052 core upgrades to the ADuC834 and ADuC836.
They include additional analog inputs for applications requiring
more ADC channels.

The ADuC845, ADuC847, and ADuC848 are complete smart
transducer front ends. The family integrates high resolution -
ADCs with flexible, up to 10-channel input multiplexing, a fast
8-bit MCU, and program/data Flash/EE memory on a single chip.

The ADuC845 includes two (primary and auxiliary) 24-bit -
ADCs with internal buffering and PGA on the primary ADC.
The ADuC847 includes the same primary ADC as the ADuC845
(auxiliary ADC removed). The ADuC848 is a 16-bit ADC
version of the ADuC847.

The ADCs incorporate flexible input multiplexing, a temperature
sensor (ADuC845 only), and a PGA (primary ADC only)
allowing direct measurement of low-level signals. The ADCs
include on-chip digital filtering and programmable output data
rates that are intended for measuring wide dynamic range, low
frequency signals, such as those in weigh scale, strain gage,
pressure transducer, or temperature measurement applications.

The devices operate from a 32 kHz crystal with an on-chip PLL
generating a high frequency clock of 12.58 MHz. This clock is
routed through a programmable clock divider from which the
MCU core clock operating frequency is generated. The micro-
controller core is an optimized single-cycle 8052 offering up to
12.58 MIPs performance while maintaining 8051 instruction set
compatibility.

The available nonvolatile Flash/EE program memory options
are 62 kbytes, 32 kbytes, and 8 kbytes. 4 kbytes of nonvolatile
Flash/EE data memory and 2304 bytes of data RAM are also
provided on-chip. The program memory can be configured as
data memory to give up to 60 kbytes of NV data memory in
data logging applications.

On-chip factory firmware supports in-circuit serial download
and debug modes (via UART), as well as single-pin emulation
mode via the EA pin. The ADuC845, ADuC847, and ADuC848
are supported by the QuickStartTM development system featuring
low cost software and hardware development tools.

ADuC845/ADuC847/ADuC848

Rev. A | Page 16 of 108

WATCHDOG

TIMER

2304 BYTES

USER RAM

POWER SUPPLY

MONITOR

TEMP

SENSOR

200

µA

200

µA

BAND GAP

REFERENCE

REF

DETECT

AGND

DGND

ESET

POR

XTA

ADuC845

ADC

PRIMARY ADC

24-BIT

- ADC

CONTROL

AND

CALIBRATION

DAC

CONTROL

12-BIT

VOLTAGE

OUTPUT DAC

T2EX

INT0

INT1

PSEN

ALE

SIN

LE-

ULATOR

TxD

4 kBYTES DATA/

FLASH/EE

62 kBYTES PROGRAM/

FLASH/EE

UART

SERIAL PORT

CURRENT

SOURCE

MIX

SINGLE-

CYCLE

8052

MCU

CORE

DOWNLOADER

DEBUGGER

SPI SERIAL

INTERFACE

16-BIT

COUNTER

TIMERS

WAKE-UP/

RTC TIMER

PLL WITH PROG.

CLOCK DIVIDER

XTA

OSC

Ч DATA POINTERS

11-BIT STACK POINTER

AIN

MUX

AIN1

AIN2

MUX

PWM0

PWM1

PWM

CONTROL

UART

TIMER

C SERIAL

INTERFACE

04741-0-004

PGA

BUF

36 51

23 37 38 50

44 43

30 31

PWMCLK

AIN3

AIN4

AIN5

AIN6

AIN7

AIN8

P0.0 (

D0)

P0.1 (

D1)

46 47

P0.2 (

D2)

P0.3 (

D3)

P0.4 (

D4)

P0.5 (

D5)

P0.6 (

D6)

P0.7 (

D7)

P3.0 (

xD)

P3.1 (

xD)

16 17

P3.2 (

I
NT0)

P3.3 (

I
NT1)

P3.4 (

P3.5 (

P3.6 (

P3.7 (

P1.0/AIN1

P1.1/AIN2

P1.2/AIN3/REFIN2+

P1.3/AIN4/REFIN2

P1.4/AIN5

P1.5/AIN6

P1.6/AIN7/IEXC1

P1.7/AIN8/IEXC2

CLK (A8

/
A1

)

P2.1/M

OSI (

9/A17)

30 31

P2.2/M

ISO (

10/A18)

P2.3/SS/T2 (

11/A

19)

P2.4/T2EX (

12/A

20)

P2.5/PW

0 (

13/A

21)

P2.6/PW

1 (

14/A

22)

P2.7/PW

(

15/A

23)

AIN9*

AIN10*

AINCOM

DUAL

16-BIT

- DAC

DUAL

16-BIT

PWM

ADC

CONTROL

AND

CALIBRATION

AUXILIARY ADC

24-BIT

- ADC

REFIN+

REFIN

IEXC1

*THE PIN NUMBERS REFER TO THE CSP PACKAGE ONLY.

SHADED AREAS ARE UPGRADES FROM THE ADuC834, AND INCLUDE A SINGLE-CYCLE CORE, UP TO 10 ADC INPUT
CHANNELS (8 ON THE MQFP PACKAGE). THE AUXILIARY ADC IS NOW 24-BIT.

Figure 4. Detailed Block Diagram of the ADuC845

ADuC845/ADuC847/ADuC848

Rev. A | Page 17 of 108

WATCHDOG

TIMER

2304 BYTES

USER RAM

POWER SUPPLY

MONITOR

200

µA

200

µA

BAND GAP

REFERENCE

REF

DETECT

AGND

ESET

POR

XTA

ADuC847

ADC

CONTROL

AND

CALIBRATION

DAC

CONTROL

12-BIT

VOLTAGE

OUTPUT DAC

T2EX

INT0

INT1

PSEN

ALE

SIN

LE-

ULATOR

TxD

4 kBYTES DATA/

FLASH/EE

62 kBYTES PROGRAM/

FLASH/EE

UART

SERIAL PORT

CURRENT

SOURCE

MIX

SINGLE-

CYCLE

8052

MCU

CORE

DOWNLOADER

DEBUGGER

SPI SERIAL

INTERFACE

16-BIT

COUNTER

TIMERS

WAKE-UP/

RTC TIMER

PLL WITH PROG.

CLOCK DIVIDER

XTA

OSC

Ч DATA POINTERS

11-BIT STACK POINTER

AIN

MUX

AIN1

AIN2

MUX

PWM0

PWM1

PWM

CONTROL

UART

TIMER

DATA

C SERIAL

INTERFACE

04741-A

-
004

PGA

BUF

36 51

DGND

37 38 50

44 43

30 31

PWMCLK

AIN3

AIN4

AIN5

AIN6

AIN7

AIN8

P0.0 (

D0)

P0.1 (

D1)

46 47

P0.2 (

D2)

P0.3 (

D3)

P0.4 (

D4)

P0.5 (

D5)

P0.6 (

D6)

P0.7 (

D7)

P3.0 (

xD)

P3.1 (

xD)

16 17

P3.2 (

I
NT0)

P3.3 (

I
NT1)

P3.4 (

P3.5 (

P3.6 (

P3.7 (

P1.0/AIN1

P1.1/AIN2

P1.2/AIN3/REFIN2+

P1.3/AIN4/REFIN2

P1.4/AIN5

P1.5/AIN6

P1.6/AIN7/IEXC1

P1.7/AIN8/IEXC2

P2.0/SC

(

8/A

16)

P2.1/M

OSI (

9/A17)

30 31

P2.2/M

ISO (

10/A18)

P2.3/SS/T2 (

11/A19)

P2.4/T2EX (

12/A

20)

P2.5/PW

0 (

13/A

21)

P2.6/PW

1 (

14/A

22)

P2.7/PW

(

15/A

23)

AIN9*

AIN10*

AINCOM

DUAL

16-BIT

- DAC

DUAL

16-BIT

PWM

REFIN+

REFIN

IEXC1

*THE PIN NUMBERS REFER TO THE CSP PACKAGE ONLY.

PRIMARY ADC

24-BIT

- ADC

SHADED AREAS ARE UPGRADES FROM THE ADuC834, AND INCLUDE A SINGLE-CYCLE CORE, UP TO 10 ADC INPUT
CHANNELS (8 ON THE MQFP PACKAGE).

Figure 5. Detailed Block Diagram of the ADuC847

ADuC845/ADuC847/ADuC848

Rev. A | Page 18 of 108

WATCHDOG

TIMER

2304 BYTES

USER RAM

POWER SUPPLY

MONITOR

200

µA

200

µA

BAND GAP

REFERENCE

REF

DETECT

AGND

DGND

ESET

POR

XTA

ADuC848

ADC

CONTROL

AND

CALIBRATION

DAC

CONTROL

12-BIT

VOLTAGE

OUTPUT DAC

T2EX

INT0

INT1

PSEN

ALE

SIN

LE-

ULATOR

TxD

4 kBYTES DATA/

FLASH/EE

62 kBYTES PROGRAM/

FLASH/EE

UART

SERIAL PORT

CURRENT

SOURCE

MIX

SINGLE-

CYCLE

8052

MCU

CORE

DOWNLOADER

DEBUGGER

SPI SERIAL

INTERFACE

16-BIT

COUNTER

TIMERS

WAKE-UP/

RTC TIMER

PLL WITH PROG.

CLOCK DIVIDER

XTA

OSC

Ч DATA POINTERS

11-BIT STACK POINTER

AIN

MUX

AIN1

AIN2

MUX

PWM0

PWM1

PWM

CONTROL

UART

TIMER

C SERIAL

INTERFACE

04741-A

-
003

PGA

BUF

36 51

23 37 38 50

44 43

30 31

PWMCLK

AIN3

AIN4

AIN5

AIN6

AIN7

AIN8

P0.0 (

D0)

P0.1 (

D1)

46 47

P0.2 (

D2)

P0.3 (

D3)

P0.4 (

D4)

P0.5 (

D5)

P0.6 (

D6)

P0.7 (

D7)

P3.0 (

xD)

P3.1 (

xD)

16 17

P3.2 (

I
NT0)

P3.3 (

I
NT1)

P3.4 (

P3.5 (

P3.6 (

P3.7 (

P1.0/AIN1

P1.1/AIN2

P1.2/AIN3/REFIN2+

P1.3/AIN4/REFIN2

P1.4/AIN5

P1.5/AIN6

P1.6/AIN7/IEXC1

P1.7/AIN8/IEXC2

CLK (A8

/
A1

)

P2.1/M

OSI (

9/A17)

30 31

P2.2/M

ISO (

10/A18)

P2.3/SS/T2 (

11/A

19)

P2.4/T2EX (

12/A

20)

P2.5/PW

0 (

13/A

21)

P2.6/PW

1 (

14/A

22)

P2.7/PW

(

15/A

23)

AIN9*

AIN10*

AINCOM

DUAL

16-BIT

- DAC

DUAL

16-BIT

PWM

REFIN+

REFIN

IEXC1

*THE PIN NUMBERS REFER TO THE CSP PACKAGE ONLY.

SHADED AREAS ARE UPGRADES FROM THE ADuC834, AND INCLUDE A SINGLE-CYCLE CORE, UP TO 10 ADC INPUT
CHANNELS (8 ON THE MQFP PACKAGE).

PRIMARY ADC

16-BIT

- ADC

Figure 6. Detailed Block Diagram of the ADuC848

8052 INSTRUCTION SET

Table 4 documents the number of clock cycles required for each
instruction. Most instructions are executed in one or two clock
cycles resulting in 12.58 MIPs peak performance when operating
at PLLCON = 00H.

TIMER OPERATION

Timers on a standard 8052 increment by one with each machine
cycle. On the ADuC845, ADuC847, and ADuC848, one machine
cycle is equal to one clock cycle; therefore, the timers increment
at the same rate as the core clock.

ALE

On the ADuC834, the output on the ALE pin is a clock at 1/6th
of the core operating frequency. On the ADuC845, ADuC847,
and ADuC848, the ALE pin operates as follows. For a single
machine cycle instruction, ALE is high for the entire machine
cycle. For a two or more machine cycle instruction, ALE is high
for the first machine cycle and then low for the remainder of
the machine cycles.

EXTERNAL MEMORY ACCESS

The ADuC845, ADuC847, and ADuC848 do not support
external program memory access, but the parts can access up to
16 MB (24 address bits) of external data memory. When
accessing external RAM, the EWAIT register might need to be
programmed in order to give extra machine cycles to MOVX
commands to allow for differing external RAM access speeds.

ADuC845/ADuC847/ADuC848

Rev. A | Page 19 of 108

COMPLETE SFR MAP

RESERVED

NOT USED

RESERVED

SPICON

F8H

05H

DACL

FBH

00H

DACH

ADuC845 ONLY

ADuC845 ONLY ADuC845 ONLY

ADuC845 ONLY

FCH

00H

DACCON

FDH

00H

RESERVED

F0H

00H

I2CADD1

F2H

7FH

RESERVED

I2CCON

E8H

00H

GN0L

GN0M

GN0H

GN1L

GN1H

E9H

xxH

EAH

xxH

EBH

xxH

ECH

xxH

EDH

xxH

RESERVED

ACC

E0H

00H

OF0L

E1H

xxH

OF0M

E2H

xxH

OF0H

E3H

xxH

OF1L

E4H

xxH

OF1H

E5H

xxH

ADC0CON2

E6H

00H

ADCSTAT

D8H

00H

ADC0L

D9H

00H

ADC0M

DAH

00H

ADC0H

DBH

00H

ADC1M

DCH

00H

ADC1H

DDH

00H

ADC1L

DEH

00H

PSW

D0H

00H

ADCMODE

D1H

08H

ADC0CON1

D2H

07H

ADC1CON

D3H

00H

D4H

45H

ICON

D5H

00H

RESERVED

T2CON

C8H

00H

RCAP2L

CAH

00H

RCAP2H

CBH

00H

TL2

CCH

00H

TH2

CDH

00H

RESERVED

WDCON

C0H

10H

B8H

00H

ECON

B9H

00H

EDATA1

BCH

00H

EDATA2

BDH

00H

A8H

00H

IEIP2

A9H

A 0H

A0H

FFH

SCON

98H

00H

SBUF

99H

00H

I2CDAT

9AH

00H

90H

FFH

TCON

88H

00H

TMOD

89H

00H

TL0

8AH

00H

TL1

8BH

00H

TH0

8CH

00H

TH1

8DH

00H

80H

FFH

81H

07H

DPL

82H

00H

DPH

83H

00H

DPP

84H

00H

RESERVED

B0H

FFH

SPIDAT

F7H

00H

RESERVED

PSMCON

DFH

DEH

EDARL

C6H

00H

EDATA3

BEH

00H

EDATA4

BFH

00H

PCON

87H

00H

ISPI

FFH

WCOL

FEH

SPE

FDH

SPIM

FCH

CPOL

FBH

CPHA

FAH

SPR1

F9H

SPR0

F8H

BITS

F7H

0 F6H

0 F5H

0 F4H

0 F3H

0 F2H

F1H

0 F0H

BITS

MDO

EFH

0 EEH

MCO

EDH

0 ECH

0 EBH

0 EAH

E9H

0 E8H

BITS

E7H

0 E6H

0 E5H

0 E4H

0 E3H

0 E2H

E1H

0 E0H

BITS

RDY0

DFH

RDY1

DEH

CAL

DDH

NOXREF

DCH

ERR0

DBH

ERR1

DAH

D9H

0 D8H

BITS

D7H

D6H

D5H

RS1

D4H

RS0

D3H

D2H

D1H

D0H

BITS

TF2

CFH

EXF2

CEH

RCLK

CDH

TCLK

CCH

EXEN2

CBH

TR2

CAH

CNT2

C9H

CAP2

C8H

BITS

PRE3

C7H

PRE2

C6H

PRE1

C5H

0 C4H

WDIR

C3H

WDS

C2H

WDE

C1H

WDWR

C0H

BITS

BFH

PADC

BEH

PT2

BDH

BCH

PT1

BBH

PX1

BAH

PT0

B9H

PX0

B8H

BITS

B7H

B6H

B5H

B4H

INT1

B3H

INT0

B2H

TxD

B1H

RxD

B0H

BITS

AFH

EADC

AEH

ET2

ADH

ACH

ET1

ABH

EX1

AAH

ET0

A9H

EX0

A8H

BITS

A7H

A6H

A5H

1 A4H

1 A3H

1 A2H

A1H

1 A0H

BITS

SM0

9FH

SM1

9EH

SM2

9DH

REN

9CH

TB8

9BH

RB8

9AH

99H

98H

BITS

97H

1 96H

1 95H

1 94H

1 93H

1 92H

T2EX

91H

90H

BITS

TF1

8FH

TR1

8EH

TF0

8DH

TR0

8CH

IE1

8BH

IT1

8AH

IE0

89H

IT0

88H

BITS

87H

1 86H

1 85H

1 84H

1 83H

1 82H

81H

1 80H

BITS

IE0

89H

IT0

88H

TCON

88H

00H

BIT MNEMONIC

BIT ADDRESS

RESET DEFAULT BIT VALUE

MNEMONIC
RESET DEFAULT VALUE

SFR ADDRESS

THESE BITS ARE CONTAINED IN THIS BYTE.

SFR MAP KEY:

SFR NOTE:
SFRs WHOSE ADDRESSES END IN 0H OR 8H ARE BIT ADDRESSABLE.

THESE SFRs MAINTAIN THEIR PRE-RESET VALUES AFTER A RESET IF TIMECON.0 = 1.

CALIBRATION COEFFICIENTS ARE PRECONFIGURED ON POWER-UP TO FACTORY CALIBRATED VALUES.

RESERVED

TIMECON HTHSEC

SEC

MIN

HOUR

INTVAL

DPCON

A1H

A2H

A3H

A4H

A5H

A6H

A7H

00H

RESERVED

PWMCON

AEH

00H

CFG845/7/8

AFH

00H

RESERVED

T3FD

T3CON

9DH

9EH

00H

EWAIT

9FH

00H

PWM0L

PWM0H

PWM1L

PWM1H

SPH

00H

B1H

B2H

B3H

B4H

B7H

RESERVED

CHIPID

C2H

A0H

EDARH

C7H

00H

MDE

I2CM

RESERVED

PRE0

PLLCON

D7H

53H

MDI

I2CRS

I2CTX

I2CI

I2CADD

9BH

55H

04741-A

-
005

NOT AVAILABLE

ON ADuC848

ADuC845 ONLY

Figure 7. Complete SFR Map for the ADuC845, ADuC847, and ADuC848

ADuC845/ADuC847/ADuC848

Rev. A | Page 20 of 108

FUNCTIONAL DESCRIPTION

8051 INSTRUCTION SET

Table 4. Optimized Single-Cycle 8051 Instruction Set

Mnemonic Description

Bytes

Cycles

Arithmetic

A A,Rn

Add register to A

ADD A,@Ri

Add indirect memory to A

ADD A,dir

Add direct byte to A

ADD A,#data

Add immediate to A

ADDC A,Rn

Add register to A with carry

ADDC A,@Ri

Add indirect memory to A with carry

ADDC A,dir

Add direct byte to A with carry

ADD A,#data

Add immediate to A with carry

SUBB A,Rn

Subtract register from A with borrow

SUBB A,@Ri

Subtract indirect memory from A with borrow

SUBB A,dir

Subtract direct from A with borrow

SUBB A,#data

Subtract immediate from A with borrow

INC A

Increment A

INC Rn

Increment register

INC @Ri

Increment indirect memory

INC dir

Increment direct byte

INC DPTR

Increment data pointer

DEC A

Decrement A

DEC Rn

Decrement register

DEC @Ri

Decrement indirect memory

DEC dir

Decrement direct byte

MUL AB

Multiply A by B

DIV AB

Divide A by B

DA A

Decimal adjust A

Logic

ANL A,Rn

AND register to A

ANL A,@Ri

AND indirect memory to A

ANL A,dir

AND direct byte to A

ANL A,#data

AND immediate to A

ANL dir,A

AND A to direct byte

ANL dir,#data

AND immediate data to direct byte

ORL A,Rn

OR register to A

ORL A,@Ri

OR indirect memory to A

ORL A,dir

OR direct byte to A

ORL A,#data

OR immediate to A

ORL dir,A

OR A to direct byte

ORL dir,#data

OR immediate data to direct byte

XRL A,Rn

Exclusive-OR register to A

XRL A,@Ri

Exclusive-OR indirect memory to A

XRL A,#data

Exclusive-OR immediate to A

XRL dir,A

Exclusive-OR A to direct byte

XRL A,dir

Exclusive-OR indirect memory to A

XRL dir,#data

Exclusive-OR immediate data to direct

CLR A

Clear A

CPL A

Complement A

SWAP A

Swap Nibbles of A

RL A

Rotate A left

ADuC845/ADuC847/ADuC848

Rev. A | Page 21 of 108

Mnemonic Description

Bytes

Cycles

RLC A

Rotate A left through carry

RR A

Rotate A right

RRC A

Rotate A right through carry

Data Transfer

MOV A,Rn

Move register to A

MOV A,@Ri

Move indirect memory to A

MOV Rn,A

Move A to register

MOV @Ri,A

Move A to indirect memory

MOV A,dir

Move direct byte to A

MOV A,#data

Move immediate to A

MOV Rn,#data

Move register to immediate

MOV dir,A

Move A to direct byte

MOV Rn, dir

Move register to direct byte

MOV dir, Rn

Move direct to register

MOV @Ri,#data

Move immediate to indirect memory

MOV dir,@Ri

Move indirect to direct memory

MOV @Ri,dir

Move direct to indirect memory

MOV dir,dir

Move direct byte to direct byte

MOV dir,#data

Move immediate to direct byte

MOV DPTR,#data

Move immediate to data pointer

MOVC A,@A+DPTR

Move code byte relative DPTR to A

MOVC A,@A+PC

Move code byte relative PC to A

MOVX

A,@Ri

Move external (A8) data to A

MOVX

A,@DPTR

Move external (A16) data to A

MOVX

@Ri,A

Move A to external data (A8)

MOVX

@DPTR,A

Move A to external data (A16)

PUSH dir

Push direct byte onto stack

POP dir

Pop direct byte from stack

XCH A,Rn

Exchange A and register

XCH A,@Ri

Exchange A and indirect memory

XCHD A,@Ri

Exchange A and indirect memory nibble

XCH A,dir

Exchange A and direct byte

Boolean

CLR C

Clear carry

CLR bit

Clear direct bit

SETB C

Set carry

SETB bit

Set direct bit

CPL C

Complement carry

CPL bit

Complement direct bit

ANL C,bit

AND direct bit and carry

ANL C,/bit

AND direct bit inverse to carry

ORL C,bit

OR direct bit and carry

ORL C,/bit

OR direct bit inverse to carry

MOV C,bit

Move direct bit to carry

MOV bit,C

Move carry to direct bit

Branching

JMP @A+DPTR

Jump indirect relative to DPTR

RET

Return from subroutine

RETI

Return from interrupt

ACALL addr11

Absolute jump to subroutine

AJMP addr11

Absolute jump unconditional

Footnotes at end of table.

ADuC845/ADuC847/ADuC848

Rev. A | Page 22 of 108

Mnemonic Description

Bytes

Cycles

SJMP rel

Short jump (relative address)

JC rel

Jump on carry = 1

JNC rel

Jump on carry = 0

JZ rel

Jump on accumulator = 0

JNZ rel

Jump on accumulator ! = 0

DJNZ Rn,rel

Decrement register, JNZ relative

LJMP

Long jump unconditional

LCALL

addr16

Long jump to subroutine

JB bit,rel

Jump on direct bit = 1

JNB bit,rel

Jump on direct bit = 0

JBC bit,rel

Jump on direct bit = 1 and clear

CJNE A,dir,rel

Compare A, direct JNE relative

CJNE A,#data,rel

Compare A, immediate JNE relative

CJNE Rn,#data,rel

Compare register, immediate JNE relative

CJNE @Ri,#data,rel

Compare indirect, immediate JNE relative

DJNZ dir,rel

Decrement direct byte, JNZ relative

Miscellaneous

NOP No

operation

One cycle is one clock.

MOVX instructions are four cycles when they have 0 wait state. Cycles of MOVX instructions are 4 + n cycles when they have n wait states as programmed via EWAIT.

LCALL instructions are three cycles when the LCALL instruction comes from an interrupt.

MEMORY ORGANIZATION

The ADuC845, ADuC847, and ADuC848 contain four memory
blocks:

· 62 kbytes/32 kbytes/8 kbytes of on-chip Flash/EE program

memory

· 4 kbytes of on-chip Flash/EE data memory
· 256 bytes of general-purpose RAM
· 2 kbytes of internal XRAM

Flash/EE Program Memory

The parts provide up to 62 kbytes of Flash/EE program memory
to run user code. All further references to Flash/EE program
memory assume the 62-kbyte option.

When EA is pulled high externally during a power cycle or a
hardware reset, the parts default to code execution from their
internal 62 kbytes of Flash/EE program memory. The parts do
not support the rollover from internal code space to external
code space. No external code space is available on the parts.
Permanently embedded firmware allows code to be serially
downloaded to the 62 kbytes of internal code space via the
UART serial port while the device is in-circuit. No external
hardware is required.

During run time, 56 kbytes of the 62-kbyte program memory
can be reprogrammed. This means that the code space can be
upgraded in the field by using a user-defined protocol running
on the parts, or it can be used as a data memory. For details, see
the Nonvolatile Flash/EE Memory section.

Flash/EE Data Memory

The user has 4 kbytes of Flash/EE data memory available that
can be accessed indirectly by using a group of registers mapped
into the special function register (SFR) space. For details, see the
Nonvolatile Flash/EE Memory section.

General-Purpose RAM

The general-purpose RAM is divided into two separate
memories, the upper and the lower 128 bytes of RAM. The
lower 128 bytes of RAM can be accessed through direct or
indirect addressing. The upper 128 bytes of RAM can be
accessed only through indirect addressing becuase it shares the
same address space as the SFR space, which must be accessed
through direct addressing.

The lower 128 bytes of internal data memory are mapped as
shown in Figure 8. The lowest 32 bytes are grouped into four
banks of eight registers addressed as R0 to R7. The next 16 bytes
(128 bits), locations 20H to 2FH above the register banks, form
a block of directly addressable bit locations at Bit Addresses
00H to 7FH. The stack can be located anywhere in the internal
memory address space, and the stack depth can be expanded up
to 2048 bytes.

Reset initializes the stack pointer to location 07H. Any call or
push pre-increments the SP before loading the stack. Therefore,
loading the stack starts from location 08H, which is also the
first register (R0) of Register Bank 1. Thus, if one is going to use
more than one register bank, the stack pointer should be
initialized to an area of RAM not used for data storage.

ADuC845/ADuC847/ADuC848

Rev. A | Page 23 of 108

07H

0FH

17H

1FH

2FH

7FH

00H

08H

10H

18H

20H

RESET VALUE OF
STACK POINTER

30H

FOUR BANKS OF EIGHT
REGISTERS
R0 TO R7

BIT-ADDRESSABLE
(BIT ADDRESSES)

GENERAL-PURPOSE
AREA

BANKS

SELECTED

VIA

BITS IN PSW

04741-0-008

Figure 8. Lower 128 Bytes of Internal Data Memory

Internal XRAM

The ADuC845, ADuC847, and ADuC848 contain 2 kbytes of
on-chip extended data memory. This memory, although on-
chip, is accessed via the MOVX instruction. The 2 kbytes of
internal XRAM are mapped into the bottom 2 kbytes of the
external address space if the CFG84x.0 (Table 7) bit is set;
otherwise, access to the external data memory occurs just like a
standard 8051.

Even with the CFG84x.0 bit set, access to the external (off chip),
XRAM occurs once the 24-bit DPTR is greater than 0007FFH.

EXTERNAL

DATA

MEMORY

SPACE

(24-BIT

ADDRESS

SPACE)

000000H

FFFFFFH

CFG845/7/8.0 = 0

EXTERNAL

DATA

MEMORY

SPACE

(24-BIT

ADDRESS

SPACE)

000000H

FFFFFFH

CFG845/7/8.0 = 1

0007FFH

000800H

2 kBYTES

ON-CHIP

XRAM

04741-0-009

Figure 9. Internal and External XRAM

When enabled and when accessing the internal XRAM, the P0
and P2 port pin operations, as well as the RD and WR strobes,
do not operate as a standard 8051 MOVX instruction. This
allows the user to use these port pins as standard I/O. The
internal XRAM can be configured as part of the extended 11-bit
stack pointer. By default, the stack operates exactly like an 8052
in that it rolls over from FFH to 00H in the general-purpose
RAM. On the ADuC845, ADuC847, and ADuC848, however, it

is possible (by setting CFG845.7/ADuC847.7/ADuC848.7) to
enable the 11-bit extended stack pointer. In this case, the stack
rolls over from FFH in RAM to 0100H in XRAM.

The 11-bit stack pointer is visible in the SPH and SP SFRs. The
SP SFR is located at 81H as with a standard 8052. The SPH SFR
is located at B7H. The 3 LSBs of the SPH SFR contain the 3
extra bits necessary to extend the 8-bit stack pointer in the SP
SFR into an 11-bit stack pointer.

UPPER 1792

BYTES OF

ON-CHIP XRAM

(DATA + STACK

FOR EXSP = 1,

DATA ONLY

FOR EXSP = 0)

256 BYTES OF

ON-CHIP DATA

RAM

(DATA +

STACK)

LOWER 256

BYTES OF

ON-CHIP XRAM

(DATA ONLY)

00H

FFH

00H

07FFH

CFG845/7/8.7 = 0

100H

04741-0-010

CFG845/7/8.7 = 1

Figure 10. Extended Stack Pointer Operation

External Data Memory (External XRAM)

There is no support for external program memory access to the
parts. However, just like a standard 8051 compatible core, the
ADuC845/ADuC847/ADuC848 can access external data
memory using a MOVX instruction. The MOVX instruction
automatically outputs the various control strobes required to
access the data memory. The parts, however, can access up to
16 Mbytes of external data memory. This is an enhancement of
the 64 kbytes of external data memory space available on a
standard 8051 compatible core. See the Hardware Design
Considerations section for details.

When accessing external RAM, the EWAIT register might need
to be programmed to give extra machine cycles to the MOVX
operation. This is to account for differing external RAM access
speeds.

EWAIT SFR

SFR Address:

9FH

Power-On Default:

00H

Bit Addressable:

This special function register (SFR), when programmed,
dictates the number of wait states for the MOVX instruction.
The value can vary between 0H and 7H. The MOVX instruction
increases by one machine cycle (4 + n, where n = EWAIT
number in decimal) for every increase in the EWAIT value.

ADuC845/ADuC847/ADuC848

Rev. A | Page 24 of 108

SPECIAL FUNCTION REGISTERS (SFRs)

The SFR space is mapped into the upper 128 bytes of internal
data memory space and accessed by direct addressing only. It
provides an interface between the CPU and all on-chip periph-
erals. A block diagram showing the programming model of the
ADuC845/ADuC847/ADuC848 via the SFR area is shown in
Figure 11.

All registers except the program counter (PC) and the four
general-purpose register banks reside in the SFR area. The SFR
registers include control, configuration, and data registers that
provide an interface between the CPU and all on-chip peripherals.

128-BYTE

SPECIAL

FUNCTION

REGISTER

AREA

62-kBYTE

ELECTRICALLY

REPROGRAMMABLE

NONVOLATILE

FLASH/EE PROGRAM

MEMORY

8051

COMPATIBLE

CORE

OTHER ON-CHIP

PERIPHERALS

TEMPERATURE

SENSOR

CURRENT SOURCES

12-BIT DAC

SERIAL I/O

WDT

PSM

TIC

PWM

- ADC

4-kBYTE

ELECTRICALLY

REPROGRAMMABLE

NONVOLATILE

FLASH/EE DATA

MEMORY

256 BYTES RAM

2kBYTES XRAM

04741-0-011

Figure 11. Programming Model

Accumulator SFR (ACC)

ACC is the accumulator register, which is used for math opera-
tions including addition, subtraction, integer multiplication and
division, and Boolean bit manipulations. The mnemonics for
accumulator-specific instructions usually refer to the accumulator
as A.

B SFR (B)

The B register is used with the accumulator for multiplication
and division operations. For other instructions, it can be treated
as a general-purpose scratch pad register.

Data Pointer (DPTR)

The data pointer is made up of three 8-bit registers: DPP (page
byte), DPH (high byte), and DPL (low byte). These provide
memory addresses for internal code and data memory access.
The DPTR can be manipulated as a 16-bit register (DPTR =
DPH, DPL), although INC DPTR instructions automatically
carry over to DPP, or as three independent 8-bit registers (DPP,
DPH, DPL).

The ADuC845/ADuC847/ADuC848 supports dual data
pointers. See the Dual Data Pointers section.

Stack Pointer (SP and SPH)

The SP SFR is the stack pointer, which is used to hold an
internal RAM address called the top of the stack. The SP register
is incremented before data is stored during PUSH and CALL
executions. Although the stack can reside anywhere in on-chip
RAM, the SP register is initialized to 07H after a reset. This
causes the stack to begin at location 08H.

As mentioned earlier, the parts offer an extended 11-bit stack
pointer. The 3 extra bits needed to make up the 11-bit stack
pointer are the 3 LSBs of the SPH byte located at B7H. To enable
the SPH SFR, the EXSP (CFG84x.7) bit must be set; otherwise,
the SPH SFR can be neither written to nor read from.

Program Status Word (PSW)

The PSW SFR contains several bits that reflect the current
status of the CPU as listed in Table 5.

SFR Address:

D0H

Power-On Default:

00H

Bit Addressable:

Yes

Table 5. PSW SFR Bit Designations

Bit No.

Name

Description

7 CY Carry

Flag.

Auxiliary Carry Flag.

5 F0 General-Purpose

Flag.

4, 3

RS1, RS0

RS1

RS0

Selected

Bank

0 0

2 OV Overflow

Flag.

1 F1 General-Purpose

Flag.

0 P Parity

Bit.

ADuC845/ADuC847/ADuC848

Rev. A | Page 25 of 108

Power Control Register (PCON)

The PCON SFR contains bits for power-saving options and
general-purpose status flags as listed in Table 6.

SFR Address:

87H

Power-On Default:

00H

Bit Addressable:

Table 6. PCON SFR Bit Designations

Bit No.

Name

Description

SMOD

Double UART Baud Rate.
0 = Normal, 1 = Double Baud Rate.

6 SERIPD

Serial Power-Down Interrupt Enable. If this
bit is set, a serial interrupt from either SPI
or I

C can terminate the power-down

mode.

INT0PD

INT0 Power-Down Interrupt Enable.
If this bit is set, either a level (IT0 = 0) or a
negative-going transition (IT0 = 1) on the
INT0 pin terminates power-down mode.

ALEOFF

If set to 1, the ALE output is disabled.

GF1

General-Purpose Flag Bit.

GF0

General-Purpose Flag Bit.

1 PD

Power-Down Mode Enable. If set to 1, the
part enters power-down mode.

-----

Not Implemented. Write Don't Care.

ADuC845/ADuC847/ADuC848 Configuration Register
(CFG845/CFG847/CFG848)

The CFG845/CFG847/CFG848 SFR contains the bits necessary
to configure the internal XRAM and the extended SP. By default,
it configures the user into 8051 mode, that is, extended SP, and
the internal XRAM are disabled. When using in a program, use
the part name only, that is, CFG845, CFG847, or CFG848.

SFR Address:

AFH

Power-On Default:

00H

Bit Addressable:

Table 7. CFG845/CFG847/CFG848 SFR Bit Designations

Bit No.

Name

Description

EXSP

Extended SP Enable.
If this bit is set to 1, the stack rolls over
from SPH/SP = 00FFH to 0100H.
If this bit is cleared to 0, SPH SFR is
disabled and the stack rolls over from
SP = FFH to SP = 00H.

----

Not Implemented. Write Don't Care.,

----

Not Implemented. Write Don't Care.

----

Not Implemented. Write Don't Care.

----

Not Implemented. Write Don't Care.

----

Not Implemented. Write Don't Care.

----

Not Implemented. Write Don't Care.

0 XRAMEN

If this bit is set to 1, the internal XRAM is
mapped into the lower 2 kbytes of the
external address space.
If this bit is cleared to 0, the internal XRAM
is accessible and up to 16 MB of external
data memory become available. See
Figure 8.

ADuC845/ADuC847/ADuC848

Rev. A | Page 26 of 108

ADC CIRCUIT INFORMATION

The ADuC845 incorporates two 10-channel (8-channel on the
MQFP package) 24-bit - ADCs, while the ADuC847 and
ADuC848 each incorporate a single 10-channel (8-channel on
the MQFP package) 24-bit and 16-bit - ADC.

Each part also includes an on-chip programmable gain
amplifier and configurable buffering (neither is available on the
auxiliary ADC on the ADuC845). The parts also incorporate
digital filtering intended for measuring wide dynamic range and
low frequency signals such as those in weigh-scale, strain-gage,
pressure transducer, or temperature measurement applications.

The ADuC845/ADuC847/ADuC848 can be configured as four
or five (MQFP/LFCSP package) fully-differential input channels
or as eight or ten (MQFP/LFCSP package) pseudo differential
input channels referenced to AINCOM. The ADC on each part
(primary only on the ADuC845) can be fully buffered internally,
and can be programmed for one of eight input ranges from
±20 mV to ±2.56 V (V

REF

Ч 1.024). Buffering the input channel

means that the part can handle significant source impedances
on the selected analog input and that RC filtering (for noise
rejection or RFI reduction) can be placed on the analog inputs.
It should be noted that if the ADC is used with internal buffering
disabled (ADC0CON1.7 = 1, ADC0CON1.6 = 0), these un-
buffered inputs provide a dynamic load to the driving source.
Therefore, resistor/capacitor combinations on the inputs can
cause dc gain errors, depending on the output impedance of the
source that is driving the ADC inputs.

Table 8 and Table 9 show the allowable external resistance/
capacitance values for unbuffered mode such that no gain error
at the 16-bit and 20-bit levels, respectively, is introduced. When
used with internal buffering enabled, it is recommended that a

capacitor (10 nF to 100 nF) be placed on the input to the ADC
(usually as part of an antialiasing filter) to aid in noise
performance.

The input channels are intended to convert signals directly from
sensors without the need for external signal conditioning. With
internal buffering disabled (relevant bits set/cleared in
ADC0CON1), external buffering might be required.

When the internal buffer is enabled, it might be necessary to
offset the negative input channel by +100 mV and to offset the
positive channel by -100 mV if the reference range is AV

This accounts for the restricted common-mode input range in
the buffer. Some circuits, for example, bridge circuits, are
inherently suitable to use without having to offset where the
output voltage is balanced around V

REF

/2 and is not sufficiently

large to encroach on the supply rails. Internal buffering is not
available on the auxiliary ADC (ADuC845 only). The auxiliary
ADC (ADuC845 only) is fixed at a gain range of ±2.50 V.

The ADCs use a - conversion technique to realize up to
24 bits on the ADuC845 and the ADuC847 and up to 16 bits on
the ADuC848 of no missing codes performance (20 Hz update
rate, chop enabled). The - modulator converts the sampled
input signal into a digital pulse train whose duty cycle contains
the digital information. A sinc

programmable low-pass filter

(see Table 28) is then used to decimate the modulator output
data stream to give a valid data conversion result at program-
mable output rates. The signal chain has two modes of operation,
chop enabled and chop disabled. The CHOP bit in the
ADCMODE register enables or disables the chopping scheme.

Table 8. Maximum Resistance for No 16-Bit Gain Error (Unbuffered Mode)

External

Capacitance

Gain

0 pF

50 pF

100 pF

500 pF

1000 pF

5000 pF

111.3 k

27.8 k

16.7 k

4.5 k

2.58 k

700

53.7 k

13.5 k

8.1 k

2.2 k

1.26 k

360

25.4 k

6.4 k

3.9 k

1.0 k

600

170

8128

10.7 k

2.9 k

1.7 k

480

270

Table 9. Maximum Resistance for No 20-Bit Gain Error (Unbuffered Mode)

External

Capacitance

Gain

0 pF

50 pF

100 pF

500 pF

1000 pF

5000 pF

84.9 k

21.1 k

12.5 k

3.2 k

1.77 k

440

42.0 k

10.4 k

6.1 k

1.6 k

880

220

20.5 k

5.0 k

2.9 k

790

430

110

8128

8.8 k

2.3 k

1.3 k

370

195

ADuC845/ADuC847/ADuC848

Rev. A | Page 27 of 108

Signal Chain Overview (Chop Enabled, CHOP = 0)

With the CHOP bit = 0 (see the ADCMODE SFR bit designa-
tions in Table 24), the chopping scheme is enabled. This is the
default condition and gives optimum performance in terms of
offset errors and drift performance. With chop enabled, the
available output rates vary from 5.35 Hz to 105 Hz (SF = 255
and 13, respectively). A typical block diagram of the ADC input
channel with chop enabled is shown in Figure 12.

The sampling frequency of the modulator loop is many times
higher than the bandwidth of the input signal. The integrator in
the modulator shapes the quantization noise (which results
from the analog-to-digital conversion) so that the noise is pushed
toward one-half of the modulator frequency. The output of the
- modulator feeds directly into the digital filter. The digital
filter then band-limits the response to a frequency significantly
lower than one-half of the modulator frequency. In this manner,
the 1-bit output of the comparator is translated into a band
limited, low noise output from the ADCs.

The ADC filter is a low-pass Sinc

or (sinx/x)

filter whose

primary function is to remove the quantization noise introduced
at the modulator. The cutoff frequency and decimated output
data rate of the filter are programmable via the Sinc filter word
loaded into the filter (SF) register (see Table 28). The complete
signal chain is chopped, resulting in excellent dc offset and
offset drift specifications and is extremely beneficial in applica-
tions where drift, noise rejection, and optimum EMI rejection
are important.

With chop enabled, the ADC repeatedly reverses its inputs. The
decimated digital output words from the Sinc

filter, therefore,

have a positive offset and a negative offset term included. As a
result, a final summing stage is included so that each output
word from the filter is summed and averaged with the previous
filter output to produce a new valid output result to be written
to the ADC data register. Programming the Sinc

decimation

factor is restricted to an 8-bit register called SF (see Table 28),
the actual decimation factor is the register value times 8.
Therefore, the decimated output rate from the Sinc

filter (and

the ADC conversion rate) is

MOD

ADC

where:
f

ADC

is the ADC conversion rate.

SF is the decimal equivalent of the word loaded to the filter
register.
f

MOD

is the modulator sampling rate of 32.768 kHz.

The chop rate of the channel is half the output data rate:

ADC

CHOP

As shown in the block diagram (Figure 12), the Sinc

filter

outputs alternately contain +V

and -V

, where V

is the

respective channel offset.

SINC

FILTER

PGA

Ч (8 Ч SF)

MOD

ADC

DIGITAL
OUTPUT

ANALOG

INPUT

MUX

BUF

AIN + V

AIN V

MOD

XOR

CHOP

04741-0-013

Figure 12. Block Diagram of the ADC Input Channel with Chop Enabled

ADuC845/ADuC847/ADuC848

Rev. A | Page 28 of 108

This offset is removed by performing a running average of 2.
This average by 2 means that the settling time to any change in
programming of the ADC is twice the normal conversion time,
while an asynchronous step change on the analog input is not
fully reflected until the third subsequent output. See Figure 13.

ADC

SETTLE

The allowable range for SF (chop enabled) is 13 to 255 with
a default of 69 (45H). The corresponding conversion rates,
rms and peak-to-peak noise performances are shown in
Table 10, Table 11, Table 12, and Table 13. The numbers are
typical and generated at a differential input voltage of 0 V
and a common-mode voltage of 2.5 V. Note that the con-
version time increases by 0.732 ms for each increment in SF.

SAMPLE 1

NO/INVALID

OUTPUT

SAMPLE 2

SAMPLE 3

SAMPLE 4

SAMPLE 5

SAMPLE 6

SAMPLE 1 + SAMPLE 2

VALID OUTPUT

SAMPLE 5 + SAMPLE 6

VALID OUTPUT

SAMPLE 2 + SAMPLE 3

VALID OUTPUT

SYNCHRONOUS CHANGE

(I.E. CHANNEL CHANGE)

SAMPLE 4 + SAMPLE 5

VALID OUTPUT

SAMPLE 3 + SAMPLE 4

NO OUTPUT

04741-0-012

Figure 13. ADC Settling Time Following a Synchronous Change with

Chop Enabled

SAMPLE 1

NO OUTPUT

SAMPLE 2

SAMPLE 3

SAMPLE 4

SAMPLE 5

SAMPLE 6

SAMPLE 1 + SAMPLE 2

VALID OUTPUT

SAMPLE 5 + SAMPLE 6

VALID OUTPUT

SAMPLE 2 + SAMPLE 3

VALID OUTPUT

ASYNCHRONOUS CHANGE

(I.E. DISCONTINUOUS INPUT CHANGE)

SAMPLE 4 + SAMPLE 5

UNSETTLED OUTPUT

SAMPLE 3 + SAMPLE 4

UNSETTLED OUTPUT

04741-0-014

Figure 14. ADC Settling Time Following an Asynchronous Change with

Chop Enabled

ADuC845/ADuC847/ADuC848

Rev. A | Page 29 of 108

ADC Noise Performance with Chop Enabled (CHOP = 0)

Table 10, Table 11, Table 12, and Table 13 show the output rms
noise and output peak-to-peak resolution in bits (rounded to
the nearest 0.5 LSB) for some typical output update rates for the
ADuC845, ADuC847, and ADuC848. The numbers are typical
and are generated at a differential input voltage of 0 V and a
common-mode voltage of 2.5 V. The output update rate is
selected via the SF7 to SF0 bits in the SF filter register. It is
important to note that the peak-to-peak resolution figures
represent the resolution for which there is no code flicker
within a 6-sigma limit.

The output noise comes from two sources. The first source is
the electrical noise in the semiconductor devices (device noise)

used in the implementation of the modulator. The second
source is quantization noise, which is added when the analog
input is converted to the digital domain. The device noise is at a
low level and is independent of frequency. The quantization
noise starts at an even lower level but rises rapidly with increasing
frequency to become the dominant noise source.

The numbers in the tables are given for the bipolar input ranges.
For the unipolar ranges, the rms noise numbers are in the same
range as the bipolar figures, but the peak-to-peak resolution is
based on half the signal range, which effectively means losing
1 bit of resolution.

Table 10. ADuC845 and ADuC847 Typical Output RMS Noise (µV) vs. Input Range and Update Rate with Chop Enabled

Input Range

SF Word

Data Update Rate (Hz)

±20 mV

±40 mV

±80 mV

±160 mV

±320 mV

±640 mV

±1.28 V

±2.56 V

105.03

1.75 1.30 1.65 1.5

2.1

3.1

7.15 13.3

59.36

1.25 0.95 1.08 0.94 1.0

1.87 3.24 7.1

27 50.56

1.0 1.0 0.85

0.85 1.13 1.56 2.9 3.6

19.79

0.63 0.68 0.52 0.7

0.61 1.1

1.3 2.75

255 5.35

0.31 0.38 0.34 0.32 0.4

0.45 0.68 1.22

Table 11. ADuC845 and ADuC847 Typical Peak-to-Peak Resolution (Bits) vs. Input Range and Update Rate with Chop Enabled

Input Range

SF Word

Data Update Rate (Hz)

±20 mV

±40 mV

±80 mV

±160 mV

±320 mV

±640 mV

±1.28 V

±2.56 V

13 105.03

12 13 14 15 15.5 16 16 16

23 59.36

12 13.5

14.5

15.5 16.5 16.5 17 16.5

50.56

12.5 13.5 15 16

16.5 17

17 17.5

69 19.79

13 14 15.5

16 17.5 17.5 18 18

255 5.35

14.5

15 16 17 18 18.5 19 19.5

Table 12. ADuC848 Typical Output Noise (µV) vs. Input Range and Update Rate with Chop Enabled

Input Range

SF Word

Data Update Rate (Hz)

±20 mV

±40 mV

±80 mV

±160 mV

±320 mV

±640 mV

±1.28 V

±2.56 V

105.03

1.75 1.30 1.65 1.5

2.1

3.1

7.15 13.3

59.36

1.25 0.95 1.08 0.94 1.0

1.87 3.24 7.1

27 50.56

1.0 1.0 0.85

0.85 1.13 1.56 2.9 3.6

19.79

0.63 0.68 0.52 0.7

0.61 1.1

1.3 2.75

255 5.35

0.31 0.38 0.34 0.32 0.4

0.45 0.68 1.22

Table 13. ADuC848 Typical Peak-to-Peak Resolution (Bits) vs. Input Range and Update Rate with Chop Enabled

Input Range

SF Word

Data Update Rate (Hz)

±20 mV

±40 mV

±80 mV

±160 mV

±320 mV

±640 mV

±1.28 V

±2.56 V

13 105.03

12 13 14 15 15.5 16 16 16

59.36

12 13.5 14.5 15.5 16

17 16

27 50.56

12.5

13.5

16 16 16 16

69 19.79

15.5

16 16 16 16

255

5.35

14.5

16 16 16 16

ADuC845/ADuC847/ADuC848

Rev. A | Page 30 of 108

Signal Chain Overview with Chop Disabled (CHOP = 1)

With CHOP = 1, chop is disabled and the available output rates
vary from 16.06 Hz to 1.365 kHz. The range of applicable SF
words is from 3 to 255. When switching between channels with
chop disabled, the channel throughput rate is higher than when
chop is enabled. The drawback with chop disabled is that the
drift performance is degraded and offset calibration is required
following a gain range change or significant temperature
change. A block diagram of the ADC input channel with chop
disabled is shown in Figure 15.

The signal chain includes a multiplex or buffer, PGA, -
modulator, and digital filter. The modulator bit stream is applied
to a Sinc

filter. Programming the Sinc

decimation factor is

restricted to an 8-bit register SF; the actual decimation factor is
the register value times 8. The decimated output rate from the
Sinc

filter (and the ADC conversion rate) is therefore

MOD

ADC

where:
f

ADC

is the ADC conversion rate.

SF is the decimal equivalent of the word loaded to the filter
register, valid range is from 3 to 255.
f

MOD

is the modulator sampling rate of 32.768 kHz.

The settling time to a step input is governed by the digital filter.
A synchronized step change requires a settling time of three
times the programmed update rate; a channel change can be
treated as a synchronized step change. This is one conversion
longer than the case for chop enabled. However, because the
ADC throughput is three times faster with chop disabled than it
is with chop enabled, the actual time to a settled ADC output is
significantly less also. This means that following a synchronized
step change, the ADC requires three conversions (note: data is
not output following a synchronized ADC change until data has
settled) before the result accurately reflects the new input
voltage.

ADC

SETTLE

An unsynchronized step change requires four conversions to
accurately reflect the new analog input at its output. Note that
with an unsynchronized change the ADC continues to output
data and so the user must take unsettled outputs into account.
Again, this is one conversion longer than with chop enabled, but
because the ADC throughput with chop disabled is faster than
with chop enabled, the actual time taken to obtain a settled
ADC output is less.

The allowable range for SF is 3 to 255 with a default of 69 (45H).
The corresponding conversion rates, rms, and peak-to-peak
noise performances are shown in Table 14, Table 15, Table 16,
and Table 17. Note that the conversion time increases by 0.244 ms
for each increment in SF.

SINC

FILTER

PGA

Ч SF

MOD

ADC

DIGITAL
OUTPUT

ANALOG

INPUT

MUX

BUF

MOD

04741-0-015

Figure 15. Block Diagram of ADC Input Channel with Chop Disabled

ADuC845/ADuC847/ADuC848

Rev. A | Page 31 of 108

ADC Noise Performance with Chop Disabled (CHOP = 1)

Table 14, Table 15, Table 16, and Table 17 show the output rms
noise and output peak-to-peak resolution in bits (rounded to
the nearest 0.5 LSB) for some typical output update rates. The
numbers are typical and are generated at a differential input
voltage of 0 V and a common-mode voltage of 2.5 V. The output
update rate is selected via the SF7 to SF0 bits in the SF filter
register. Note that the peak-to-peak resolution figures represent
the resolution for which there is no code flicker within a 6-
sigma limit.

The output noise comes from two sources. The first source is
the electrical noise in the semiconductor devices (device noise)
used in the implementation of the modulator. The second

source is quantization noise, which is added when the analog
input is converted to the digital domain. The device noise is at a
low level and is independent of frequency. The quantization
noise starts at an even lower level but rises rapidly with increasing
frequency to become the dominant noise source.

The numbers in the tables are given for the bipolar input ranges.
For the unipolar ranges, the rms noise numbers are the same as
the bipolar range, but the peak-to-peak resolution is based on
half the signal range, which effectively means losing 1 bit of
resolution. Typically, the performance of the ADC with chop
disabled shows a 0.5 LSB degradation over the performance
with chop enabled.

Table 14. ADuC845 and ADuC847 Typical Output RMS Noise (µV) vs. Input Range and Update Rate with Chop Disabled

Table 15. ADuC845 and ADuC847 Typical Peak-to-Peak Resolution (Bits) vs. Input Range and Update Rate with Chop Disabled

Table 16. ADuC848 Typical Output RMS Noise (µV) vs. Input Range and Update Rate with Chop Disabled

Table 17. ADuC848 Typical Peak-to-Peak Resolution (Bits) vs. Input Range and Update Rate with Chop Disabled

Input Range

SF Word

Data Update Rate
(Hz)

±20 mV

±40 mV

±80 mV

±160 mV

±320mV

±640mV

±1.28 V

±2.56 V

3 1365.33

7.5

9 9 9 9 9 9

13 315.08

11.5 12.5 13.5 14

13.5 14 14

68 59.36

13 14 14.5

15.5 16 16 16

82 49.95

13 14 15 16 16 16 16

255 16.06

13.5 14.5 15.5 16

16 16

Input Range

SF Word

Data Update
Rate (Hz)

±20 mV

±40 mV

±80 mV

±160 mV

±320 mV

±640 mV

±1.28 V

±2.56 V

1365.33

30.64 24.5 56.18 100.47 248.39 468.65 774.36

1739.5

13 315.08

2.07

1.95

2.28

3.24 8.22 13.9 20.98

49.26

68 59.36

0.85

0.79

1.01

0.99 0.79 1.29 2.3 3.7

82 49.95

0.83

0.77

0.85

0.77 0.91 1.12 1.59

3.2

255 16.06

0.52

0.58

0.59

0.48 0.52 0.57 1.16

1.68

Input Range

SF Word

Data Update
Rate (Hz)

±20 mV

±40 mV

±80 mV

±160 mV

±320 mV

±640 mV

±1.28 V

±2.56 V

3 1365.33 7.5

9 9 9 9

315.08

11.5 12.5 13.5 14

13.5 14

14 14

68 59.36

14.5

15.5

17 17 17.5

82 49.95

13 14 15 16 16.5 17.5 18 18

255 16.06

13.5

14.5

15.5

16.5 17.5 18.5 18.5

Input Range

SF Word

Data Update
Rate (Hz)

±20 mV

±40 mV

±80 mV

±160 mV

±320 mV

±640 mV

±1.28 V

±2.56 V

1365.33

30.64 24.5 56.18 100.47 248.39 468.65 774.36

1739.5

13 315.08

2.07

1.95

2.28

3.24 8.22 13.9 20.98

49.26

69 59.36

0.85

0.79

1.01

0.99 0.79 1.29 2.3 3.7

82 49.95

0.83

0.77

0.85

0.77 0.91 1.12 1.59

3.2

255 16.06

0.52

0.58

0.59

0.48 0.52 0.57 1.16

1.68

ADuC845/ADuC847/ADuC848

Rev. A | Page 32 of 108

AUXILIARY ADC (ADUC845 ONLY)

Table 18. ADuC845 Typical Output RMS Noise (µV) vs.
Update Rate with Chop Enabled

SF Word

Data Update Rate (Hz)

µV

13 105.03

17.46

23 59.36

3.13

27 50.56

4.56

69 19.79

2.66

255 5.35

1.13

Table 19. ADuC845 Typical Peak-to-Peak Resolution (Bits) vs.
Update Rate

with Chop Enabled

SF Word

Data Update Rate (Hz)

Bits

13 105.03

15.5

23 59.36

27 50.56

17.5

69 19.79

255 5.35

19.5

ADC converting in bipolar mode.

Table 20. ADuC845 Typical Output RMS Noise (µV) vs.
Update Rate with Chop Disabled

SF Word

Data Update Rate (Hz)

µV

3 1365.33

1386.58

13 315.08

34.94

66 62.06

3.2

69 59.36

3.19

81 50.57

3.14

255 16.06

1.71

Table 21. ADuC845 Peak-to-Peak Resolution (Bits) vs.
Update Rate with Chop Disabled

SF Word

Data Update Rate (Hz)

Bits

3 1365.33

13 315.08

14.5

66 62.06

69 59.36

81 50.57

255 16.06

REFERENCE INPUTS

The ADuC845/ADuC847/ADuC848 each have two separate
differential reference inputs, REFIN± and REFIN2±. While both
references are available for use with the primary ADC, only
REFIN± is available for the auxiliary ADC (ADuC845 only).
The common-mode range for these differential references is
from AGND to AV

. The nominal external reference voltage is

2.5 V, with the primary and auxiliary (ADuC845 only)

reference

select bits configured from the ADC0CON2 and ADC1CON
(ADuC845 only), respectively.

When an external reference voltage is used, the primary ADC
sees this internally as a 2.56 V reference (V

REF

Ч 1.024).

Therefore, any calculations of LSB size should account for this.
For instance, with a 2.5 V external reference connected and
using a gain of 1 on a unipolar range (2.56 V), the LSB size is
(2.56/2

) = 152.6 nV (if using the 24-bit ADC on the ADuC845

or ADuC847). If a bipolar gain of 4 is used (±640 mV), the LSB
size is (±640 mV)/2

) = 76.3 nV (again using the 24-bit ADC

on the ADuC845 or ADuC847).

The ADuC845/ADuC847/ADuC848 can also be configured to
use the on-chip band gap reference via the XREF0/1 bits in the
ADC0CON2 SFR (for primary ADC) or the AXREF bit in
ADC1CON (for auxiliary ADC (ADuC845 only)). In this mode
of operation, the ADC sees the internal reference of 1.25 V,
thereby halving all the input ranges. A consequence of using the
internal band gap reference is a noticeable degradation in peak-
to-peak resolution. For this reason, operation with an external
reference is recommended.

In applications where the excitation (voltage or current) for the
transducer on the analog input also drives the reference inputs
for the part, the effect of any low frequency noise in the
excitation source is removed because the application is ratio-
metric. If the parts are not used in a ratiometric configuration, a
low noise reference should be used. Recommended reference
voltage sources for the ADuC845/ADuC847/ADuC848 include
ADR421, REF43, and REF192.

The reference inputs provide a high impedance, dynamic load
to external connections. Because the impedance of each reference
input is dynamic, resistor/capacitor combinations on these pins
can cause dc gain errors, depending on the output impedance of
the source that is driving the reference inputs. Reference voltage
sources, such as those mentioned above, for example, the ADR421,
typically have low output impedances, and, therefore, decoupling
capacitors on the REFIN± or REFIN2± inputs would be recom-
mended (typically 0.1 µF). Deriving the reference voltage from
an external resistor configuration means that the reference input
sees a significant external source impedance. External decoupling
of the REFIN± and/or REFIN2± inputs is not recommended in
this type of configuration.

BURNOUT CURRENT SOURCES

The primary ADC on the ADuC845 and the ADC on the
ADuC847 and ADuC848 incorporate two 200 µA constant
current generators, one sourcing current from the AV

AIN(+), and one sinking current from AIN(-) to AGND. These
currents are only configurable for use on AIN4 to AIN5 and/or
AIN6 to AIN7 in differential mode only, from the ICON.6 bit in
the ICON SFR (see Table 30). These burnout current sources are
also available only with buffering enabled via the BUF0/BUF1 bits
in the ADC0CON1 SFR. Once the burnout currents are turned
on, a current flows in the external transducer circuit, and a
measurement of the input voltage on the analog input channel

ADuC845/ADuC847/ADuC848

Rev. A | Page 33 of 108

can be taken. When the resulting voltage measured is full scale,
the transducer has gone open circuit. When the voltage measured
is 0 V, this indicates that the transducer has gone short circuit.
The current sources work over the normal absolute input
voltage range specifications.

REFERENCE DETECT CIRCUIT

The main and auxiliary (ADuC845 only) ADCs can be
configured to allow the use of the internal band gap reference or
an external reference that is applied to the REFIN± pins by
means of the XREF0/1 bit in the Control Registers AD0CON2
and AD1CON (ADuC845 only). A reference detection circuit is
provided to detect whether a valid voltage is applied to the
REFIN± pins. This feature arose in connection with strain-gage
sensors in weigh scales where the reference and signal are
provided via a cable from the remote sensor. It is desirable to
detect whether the cable is disconnected. If either of the pins is
floating or if the applied voltage is below a specified threshold, a
flag (NOXREF) is set in the ADC status register (ADCSTAT),
conversion results are clamped, and calibration registers are not
updated if a calibration is in progress.

Note that the reference detect does not look at REFIN2± pins.

If, during either an offset or gain calibration, the NOEXREF bit
becomes active, indicating a incorrect V

REF

, updating the relevant

calibration register is inhibited to avoid loading incorrect data
into these registers, and the appropriate bits in ADCSTAT (ERR0
or ERR1) are set. If the user needs to verify that a valid
reference is in place every time a calibration is performed, the
status of the ERR0 and ERR1 bits should be checked at the end
of every calibration cycle.

SINC FILTER REGISTER (SF)

The number entered into the SF register sets the decimation
factor of the Sinc

filter for the ADC. See Table 28 and Table 29.

The range of operation of the SF word depends on whether
ADC chop is on or off. With chop disabled, the minimum SF
word is 3 and the maximum is 255. This gives an ADC through-
put rate from 16.06 Hz to 1.365 kHz. With chop enabled, the
minimum SF word is 13 (all values lower than 13 are clamped
to 13) and the maximum is 255. This gives an ADC throughput
rate of from 5.4 Hz to 105 Hz. See the f

ADC

equation in the ADC

description preceding section.

An additional feature of the Sinc

filter is a second notch filter

positioned in the frequency response at 60 Hz. This gives
simultaneous 60 Hz rejection to whatever notch is defined by
the SF filter. This 60 Hz filter is enabled via the REJ60 bit in the
ADCMODE register (ADCMODE.6). The notch is valid only
for SF words 68; otherwise, ADC errors occur, and, in fact, the
notch is best used with an SF word of 82d giving simultaneous
50 Hz and 60 Hz rejection. This function is useful only with an

ADC clock (modulator rate) of 32.768 kHz. During calibration,
the current (user-written) value of the SF register is used.

MODULATOR

A - ADC usually consists of two main blocks, an analog
modulator, and a digital filter. For the ADuC845/ADuC847/
ADuC848, the analog modulator consists of a difference
amplifier, an integrator block, a comparator, and a feedback
DAC as shown in Figure 16.

INTEGRATOR

COMPARATOR

DIFFERENCE

AMP

ANALOG

INPUT

HIGH
FREQUENCY
BIT STREAM
TO DIGITAL
FILTER

DAC

04741-0-016

Figure 16. - Modulor Simplified Block Diagram

In operation, the analog signal is fed to the difference amplifier
along with the output from the feedback DAC. The difference
between these two signals is integrated and fed to the comparator.
The output from the comparator provides the input to the feed-
back DAC so the system functions as a negative feedback loop
that tries to minimize the difference signal. The digital data that
represents the analog input voltage is contained in the duty
cycle of the pulse train appearing at the output of the comparator.
This duty cycle data can be recovered as a data-word by using a
subsequent digital filter stage. The sampling frequency of the
modulator loop is many times higher than the bandwidth of the
input signal. The integrator in the modulator shapes the
quantization noise (that results from the analog-to-digital
conversion) so that the noise is pushed toward one-half of the
modulator frequency.

DIGITAL FILTER

The output of the - modulator feeds directly into the digital
filter. The digital filter then band-limits the response to a
frequency significantly lower than one-half of the modulator
frequency. In this manner, the 1-bit output of the comparator is
translated into a band-limited, low noise output from the part.

The ADuC845/ADuC847/ADuC848 filter is a low-pass, Sinc

[(SINx)/x]

filter whose primary function is to remove the

quantization noise introduced at the modulator. The cutoff
frequency and decimated output data rate of the filter are
programmable via the SF (Sinc filter) SFR as listed in Table 28
and Table 29.

Figure 22, Figure 23, Figure 24, and Figure 25 show the frequency
response of the ADC, yielding an overall output rate of 16.6 Hz
with chop enabled and 50 Hz with chop disabled. Also detailed
in these plots is the effect of the fixed 60 Hz drop-in notch filter
(REJ60 bit, ADCMODE.6). This fixed filter can be enabled or
disabled by setting or clearing the REJ60 bit in the ADCMODE
register (ADCMODE.6). This 60 Hz drop-in notch filter can be

ADuC845/ADuC847/ADuC848

Rev. A | Page 34 of 108

enabled for any SF word that yields an ADC throughput that is
less than 20 Hz with chop enabled (SF 68 decimal).

ADC CHOPPING

The ADCs on the ADuC845/ADuC847/ADuC848 implement a
chopping scheme whereby the ADC repeatedly reverses its inputs.
The decimated digital output words from the Sinc

filter, there-

fore, have a positive and negative offset term included. As a
result, a final summing stage is included in each ADC so that
each output word from the filter is summed and averaged with
the previous filter output to produce a new valid output result
to be written to the ADC data SFRs. The ADC throughput or
update rate is listed in Table 29. The chopping scheme incor-
porated into the parts results in excellent dc offset and offset
drift specifications and is extremely beneficial in applications
where drift, noise rejection, and optimum EMI performance are
important. ADC chop can be disabled via the chop bit in the
ADCMODE SFR (ADCMODE.3). Setting this bit to 1 (logic
high) disables chop mode.

CALIBRATION

The ADuC845/ADuC847/ADuC848 incorporate four calibration
modes that can be programmed via the mode bits in the
ADCMODE SFR detailed in Table 24. Every part is calibrated
before it leaves the factory. The resulting offset and gain
calibration coefficients for both the primary and auxiliary
(ADuC845 only) ADCs are stored on-chip in manufacturing-
specific Flash/EE memory locations. At power-on or after a
reset, these factory calibration registers are automatically
downloaded to the ADC calibration registers in the part's SFR
space. To facilitate user calibration, each of the primary and
auxiliary (ADuC845 only) ADCs have dedicated calibration
control SFRs, which are described in the ADC SFR Interface
section. Once a user initiates a calibration procedure the factory
calibration values that were initially downloaded during the
power-on sequence to the ADC calibration SFRs are overwritten.
The ADC to be calibrated must be enabled via the ADC enable
bits in the ADCMODE register.

Even though an internal offset calibration mode is described in
this section, note that the ADCs can be chopped. This chopping
scheme inherently minimizes offset errors and means that an
offset calibration should never be required. Also, because
factory 5 V/25°C gain calibration coefficients are automatically
present at power-on, an internal full-scale calibration is required
only if the part is operated at 3 V or at temperatures significantly
different from 25°C.

If the part is operated in chop disabled mode, a calibration may
need to be done with every gain range change that occurs via
the PGA.

The ADuC845/ADuC847/ADuC848 each offer internal or
system calibration facilities. For full calibration to occur on the
selected ADC, the calibration logic must record the modulator

output for two input conditions: zero-scale and full-scale points.
These points are derived by performing a conversion on the
different input voltages (zero-scale and full-scale) provided to the
input of the modulator during calibration. The result of the
zero-scale calibration conversion is stored in the offset
calibration registers for the appropriate ADC. The result of the
full-scale calibration conversion is stored in the gain calibration
registers for the appropriate ADC. With these readings, the
calibration logic can calculate the offset and the gain slope for
the input-to-output transfer function of the converter.

During an internal zero-scale or full-scale calibration, the
respective zero-scale input or full-scale input is automatically
connected to the ADC inputs internally. A system calibration,
however, expects the system zero-scale and system full-scale
voltages to be applied externally to the ADC pins by the user
before the calibration mode is initiated. In this way, external
errors are taken into account and minimized. Note that all
ADuC845/ADuC847/ADuC848 ADC calibrations are carried
out at the user-selected SF word update rate. To optimize
calibration accuracy, it is recommended that the slowest possible
update rate be used.

Internally in the parts, the coefficients are normalized before
being used to scale the words coming out of the digital filter.
The offset calibration coefficient is subtracted from the result
prior to the multiplication by the gain coefficient.

From an operational point of view, a calibration should be
treated just like an ordinary ADC conversion. A zero-scale
calibration (if required) should always be carried out before a
full-scale calibration. System software should monitor the
relevant ADC RDY0/1 bit in the ADCSTAT SFR to determine
the end of calibration by using a polling sequence or an interrupt
driven routine. If required, the NOEXREF0/1 bits can be moni-
tored to detect unconnected or low voltage errors in the reference
during conversion. In the event of the reference becoming
disconnected, causing a NOXREF flag during a calibration, the
calibration is immediately halted and no write to the calibration
SFRs takes place.

Internal Calibration Example

With chop enabled, a zero-scale or offset calibration should
never be required, although a full-scale or offset calibration may
be required. However, if a full internal calibration is required,
the procedure should be to select a PGA gain of 1 (±2.56 V) and
perform a zero-scale calibration (MD2...0 = 100B in the
ADCMODE register). Next, select and perform full-scale
calibration by setting MD2...0 = 101B in the ADCMODE SFR.
Now select the desired PGA range and perform a zero-scale
calibration again (MD2..0 = 100B in ADCMODE) at the new
PGA range. The reason for the double zero-scale calibration is
that the internal calibration procedure for full-scale calibration
automatically selects the reference in voltage at PGA = 1.
Therefore, the full-scale endpoint calibration automatically

ADuC845/ADuC847/ADuC848

Rev. A | Page 35 of 108

subtracts the offset calibration error, it is advisable to perform
an offset calibration at the same gain range as that used for full-
scale calibration. There is no penalty to the full-scale calibration
in redoing the zero-scale calibration at the required PGA range
because the full-scale calibration has very good matching at all
the PGA ranges.

This procedure also applies when chop is disabled.

Note that for internal calibration to be effective, the AIN- pin
should be held at a steady voltage, within the allowable common-
mode range to keep it from floating during calibration.

System Calibration Example

With chop enabled, a system zero-scale or offset calibration
should never be required. However, if a full-scale or gain
calibration is required for any reason, use the following typical
procedure for doing so.

1. Apply a differential voltage of 0 V to the selected analog

inputs (AIN+ to AIN-) that are held at a common-mode
voltage.

Perform a system zero-scale or offset calibration by setting
the MD2...0 bits in the ADCMODE register to 110B.

2. Apply a full-scale differential voltage across the ADC

inputs again at the same common-mode voltage.

Perform a system full-scale or gain calibration by setting
the MD2...0 bits in the ADCMODE register to 111B.

Perform a system calibration at the required PGA range to be
used since the ADC scales to the differential voltages that are
applied to the ADC during the calibration routines.

In bipolar mode, the zero-scale calibration determines the mid-
scale point of the ADC (800000H) or 0 V.

PROGRAMMABLE GAIN AMPLIFIER

The primary ADC incorporates an on-chip programmable gain
amplifier (PGA). The PGA can be programmed through eight
different ranges, which are programmed via the range bits (RN0
to RN2) in the ADC0CON1 register. With an external 2.5 V
reference applied, the unipolar ranges are 0 mV to 20 mV, 0 mV
to 40 mV, 0 mV to 80 mV, 0 mV to 160 mV, 0 mV to 320 mV,
0 mV to 640 mV, 0 V to 1.28 V and 0 V to 2.56 V, while in
bipolar mode the ranges are ±20 mV, ±40 mV, ±80 mV, ±160 mV,
±320 mV, ±64 0 mV, ±1.28 V, and ±2.56 V. These ranges should
appear on the input to the on-chip PGA. The ADC range-
matching specification of 2 µV (typical with chop enabled)
means that calibration need only be carried out on a single
range and need not be repeated when the ADC range is
changed. This is a significant advantage compared to similar

mixed-signal solutions available on the market. The auxiliary
(ADuC845 only) ADC does not incorporate a PGA, and the
gain is fixed at 0 V to 2.50 V in unipolar mode, and ±2.50 V in
bipolar mode.

BIPOLAR/UNIPOLAR CONFIGURATION

The analog inputs of the ADuC845/ADuC847/ADuC848 can
accept either unipolar or bipolar input voltage ranges. Bipolar
input ranges do not imply that the part can handle negative
voltages with respect to system AGND, but rather with respect
to the negative reference input. Unipolar and bipolar signals on
the AIN(+) input on the ADC are referenced to the voltage on
the respective AIN(-) input. AIN(+) and AIN(-) refer to the
signals seen by the ADC.

For example, if AIN(-) is biased to 2.5 V (tied to the external
reference voltage) and the ADC is configured for a unipolar
analog input range of 0 mV to > 20 mV, the input voltage range
on AIN(+) is 2.5 V to 2.52 V. On the other hand, if AIN(-) is
biased to 2.5 V (again the external reference voltage) and the
ADC is configured for a bipolar analog input range of ±1.28 V,
the analog input range on the AIN(+) is 1.22 V to 3.78 V, that is,
2.5 V ± 1.28 V.

The modes of operation for the ADC are fully differential mode
or pseudo differential mode. In fully differential mode, AIN1 to
AIN2 are one differential pair, AIN3 to AIN4 are another pair
(AIN5 to AIN6, AIN7 to AIN8, and AIN9 to AIN10 are the
others). In differential mode, all AIN(-) pin names imply the
negative analog input of the selected differential pair, that is,
AIN2, AIN4, AIN6, AIN8, AIN10. The term AIN(+) implies the
positive input of the selected differential pair, that is, AIN1,
AIN3, AIN5, AIN7, AIN9. In pseudo differential mode, each
analog input is paired with the AINCOM pin, which can be
biased up or tied to AGND. In this mode, the AIN(-) implies
AINCOM and AIN(+) implies any one of the ten analog input
channels.

The configuration of the inputs (unipolar versus bipolar) is
shown in Figure 17.

AIN1

INP

T 1

ADuC845/

ADuC847/

ADuC848

CSP PACKAGE

ADuC845/

ADuC847/

ADuC848

CSP PACKAGE

INP

T 2

INP

T 3

INP

T 4

INP

T 5

INP

T 6

INP

T 7

INP

T 8

INP

T 9

INP

T 1

AIN2

AIN3

AIN4

AIN5

AIN6

AIN7

AIN8

AIN9

AIN10

AINCOM

AIN1

AIN2

AIN3

AIN4

AIN5

AIN6

AIN7

AIN8

AIN9

AIN10

FULLY DIFFERENTIAL

AINCOM

04741-0-017

Figure 17. Unipolar and Bipolar Channel Pairs

ADuC845/ADuC847/ADuC848

Rev. A | Page 36 of 108

DATA OUTPUT CODING

When the primary ADC is configured for unipolar operation,
the output coding is natural (straight) binary with a zero differ-
ential input voltage resulting in a code of 000...000, a midscale
voltage resulting in a code of 100...000, and a full-scale voltage
resulting in a code of 111...111. The output code for any analog
input voltage on the main ADC can be represented as follows:

Code (AIN Ч GAIN Ч 2

) / (1.024 Ч V

REF

)

where:

AIN is the analog input voltage.
GAIN is the PGA gain setting, that is, 1 on the 2.56 V range and
128 on the 20 mV range, and N = 24 (16 on the ADuC848).

The output code for any analog input voltage on the auxiliary
ADC can be represented as follows:

Code = (AIN Ч 2

) / (V

REF

)

with the same definitions as used for the primary ADC above.

When the primary ADC is configured for bipolar operation, the
coding is offset binary with negative full-scale voltage resulting
in a code of 000...000, a zero differential voltage resulting in a
code of 800...000, and a positive full-scale voltage resulting in a
code of 111...111. The output from the primary ADC for any
analog input voltage can be represented as follows:

Code = 2

N-1

[(AIN Ч GAIN) / (1.024 ЧV

REF

) + 1]

where:

AIN is the analog input voltage.
GAIN is the PGA gain, that is, 1 on the ±2.56 V range and
128 on the ±20 mV range.
N = 24 (16 on the ADuC848).

The output from the auxiliary ADC in bipolar mode can be
represented as follows:

Code = 2

N-1

[(AIN / V

REF

) + 1]

EXCITATION CURRENTS

The ADuC845/ADuC847/ADuC848 contain two matched,
software-configurable 200 µA current sources. Both source
current from AV

, which is directed to either or both of the

IEXC1 (Pin 11 whose alternate functions are P1.6/AIN6) or
IEXC2 (Pin 12, whose alternate functions are P1.7/AIN7) pins
on the device. These currents are controlled via the lower four
bits in the ICON register (Table 30). These bits not only enable
the current sources but also allow the configuration of the
currents such that 200 µA can be sourced individually from
both pins or can be combined to give a 400 µA source from one
or the other of the outputs. These sources can be used to excite
external resistive bridge or RTD sensors (see Figure 70).

ADC POWER-ON

The ADC typically takes 0.5 ms to power up from an initial
start-up sequence or following a power-down event.

ADuC845/ADuC847/ADuC848

Rev. A | Page 37 of 108

TYPICAL PERFORMANCE CHARACTERISTICS

120

110

100

80

70

50

40

20

10

90

30

60

100

110

FREQUENCY (Hz)

GAIN (

04741-0-018

Figure 18. Filter Response, Chop On, SF = 69 Decimal

150

130

110

90

50

30

10

70

100

FREQUENCY (Hz)

AMP

ITUDE

(dB)

04741-0-019

Figure 19. Filter Response, Chop On, SF = 255 Decimal

120

110

100

80

70

50

40

20

10

90

30

60

90 110

210

190

170

230

150

130

250

SF (Decimal)

GAIN (

04741-0-020

Figure 20. 50 Hz Normal Mode Rejection vs. SF Word, Chop On

120

110

100

80

70

50

40

20

10

90

30

60

90 110

210

190

170

230

150

130

250

SF (Decimal)

GAIN (

04741-0-021

Figure 21. 60 Hz Normal Mode Rejection vs. SF, Chop On

150

130

110

90

50

30

10

70

170.1

160.1

150.1

140.1

130.1

120.1

110.1

100.1

90.1

80.1

70.1

60.1

50.1

40.1

30.1

20.1

10.1

0.1

FREQUENCY (Hz)

AMP

ITUDE

(dB)

04741-0-022

Figure 22. Chop Off, Fadc = 50 Hz, SF = 52H

150

130

110

50

10

30

70

190

170.1

160.1

150.1

140.1

130.1

120.1

110.1

100.1

90.1

80.1

70.1

60.1

50.1

40.1

30.1

20.1

10.1

0.1

FREQUENCY (Hz)

AMP

ITUDE

(dB)

04741-0-023

Figure 23. Chop Off, SF = 52H, REJ60 Enabled

ADuC845/ADuC847/ADuC848

Rev. A | Page 39 of 108

FUNCTIONAL DESCRIPTION

ADC SFR INTERFACE

The ADCs are controlled and configured via a number of SFRs that are mentioned here and described in more detail in the following
sections.

Table 22. ADC SFR Interface

Name Description

ADCSTAT

ADC Status Register. Holds the general status of the primary and auxiliary (ADuC845 only) ADCs.

ADCMODE

ADC Mode Register. Controls the general modes of operation for primary and auxiliary (ADuC845 only) ADCs.

ADC0CON1

Primary ADC Control Register 1. Controls the specific configuration of the primary ADC.

ADC0CON2

Primary ADC Control Register 2. Controls the specific configuration of the primary ADC.

ADC1CON

Auxiliary ADC Control Register. Controls the specific configuration of the auxiliary ADC. ADuC845 only.

Sinc Filter Register. Configures the decimation factor for the Sinc

filter and, therefore, the primary and auxiliary (ADuC845

only) ADC update rates.

ICON

Current Source Control Register. Allows user control of the various on-chip current source options.

ADC0L/M/H

Primary ADC 24-bit (16-bit on the ADuC848) conversion result is held in these three 8-bit registers. ADC0L is not available on
the ADuC848.

ADC1L/M/H

Auxiliary ADC 24-bit conversion result is held in these two 8-bit registers. ADuC845 only.

OF0L/M/H

Primary ADC 24-bit offset calibration coefficient is held in these three 8-bit registers. OF0L is not available on the ADuC848.

OF1L/H

Auxiliary ADC 16-bit offset calibration coefficient is held in these two 8-bit registers. ADuC845 only.

GN0L/M/H

Primary ADC 24-bit gain calibration coefficient is held in these three 8-bit registers. GN0L is not available on the ADuC848.

GN1L/H

Auxiliary ADC 16-bit gain calibration coefficient is held in these two 8-bit registers. ADuC845 only.

ADuC845/ADuC847/ADuC848

Rev. A | Page 40 of 108

ADCSTAT (ADC STATUS REGISTER)

This SFR reflects the status of both ADCs including data ready, calibration, and various (ADC-related) error and warning conditions
including REFIN± reference detect and conversion overflow/underflow flags.

SFR Address:

D8H

Power-On Default:

00H

Bit Addressable:

Yes

Table 23. ADCSTAT SFR Bit Designation

Bit No.

Name

Description

RDY0

Ready Bit for the Primary ADC.
Set by hardware on completion of conversion or calibration.
Cleared directly by the user or indirectly by a write to the mode bits to start calibration. The primary ADC is
inhibited from writing further results to its data or calibration registers until the RDY0 bit is cleared.

RDY1

Ready Bit for Auxiliary (ADuC845 only) ADC.
Same definition as RDY0 referred to the auxiliary ADC. Valid on the ADuC845 only.

CAL

Calibration Status Bit.
Set by hardware on completion of calibration.
Cleared indirectly by a write to the mode bits to start another ADC conversion or calibration.
Note that calibration with the temperature sensor selected (auxiliary ADC on the ADuC845 only) fails to complete.

NOXREF

No External Reference Bit (only active if primary or auxiliary (ADuC845 only) ADC is active).
Set to indicate that one or both of the REFIN pins is floating or the applied voltage is below a specified threshold.
When set, conversion results are clamped to all 1s. Only detects invalid REFIN±, does not check REFIN2±.
Cleared to indicate valid V

REF

ERR0

Primary ADC Error Bit.
Set by hardware to indicate that the result written to the primary ADC data registers has been clamped to all 0s or
all 1s. After a calibration, this bit also flags error conditions that caused the calibration registers not to be written.
Cleared by a write to the mode bits to initiate a conversion or calibration.

ERR1

Auxiliary ADC Error Bit. Same definition as ERR0 referred to the auxiliary ADC. Valid on the ADuC845 only.

Not Implemented. Write Don't Care.

ADuC845/ADuC847/ADuC848

Rev. A | Page 41 of 108

ADCMODE (ADC MODE REGISTER)

Used to control the operational mode of both ADCs.

SFR Address:

D1H

Power-On Default:

08H

Bit Addressable:

Table 24. ADCMODE SFR Bit Designations

Bit No.

Name

Description

Not Implemented. Write Don't Care.

REJ60

Automatic 60 Hz Notch Select Bit.
Setting this bit places a notch in the frequency response at 60 Hz, allowing simultaneous 50 Hz and 60 Hz
rejection at an SF word of 82 decimal. This 60 Hz notch can be set only if SF 68 decimal, that is, the regular
filter notch must be

60 Hz. This second notch is placed at 60 Hz only if the device clock is at 32.768 kHz.

ADC0EN

Primary ADC Enable.
Set by the user to enable the primary ADC and place it in the mode selected in MD2MD0 below.
Cleared by the user to place the primary ADC into power-down mode.

ADC1EN
(ADuC845 only)

Auxiliary (ADuC845 only) ADC Enable.
Set by the user to enable the auxiliary (ADuC845 only) ADC and place it in the mode selected in MD2MD0
below.
Cleared by the user to place the auxiliary (ADuC845 only) ADC in power-down mode.

CHOP

Chop Mode Disable.
Set by the user to disable chop mode on both the primary and auxiliary (ADuC845 only) ADC allowing a
three times higher ADC data throughput. SF values as low as 3 are allowed with this bit set, giving up to
1.3 kHz ADC update rates.
Cleared by the user to enable chop mode on both the primary and auxiliary (ADuC845 only) ADC.
Primary and Auxiliary (ADuC845 only) ADC Mode Bits.
These bits select the operational mode of the enabled ADC as follows:
MD2 MD1 MD0

ADC Power-Down Mode (Power-On Default).

0 0 1 Idle Mode. In idle mode, the ADC filter and modulator are held in a reset state

although the modulator clocks are still provided.

0 1 0 Single Conversion Mode. In single conversion mode, a single conversion is performed

on the enabled ADC. Upon completion of a conversion, the ADC data registers
(ADC0H/M/L and/or ADC1H/M/L (ADuC845 only)) are updated. The relevant flags in
the ADCSTAT SFR are written, and power-down is re-entered with the MD2-MD0
accordingly being written to 000.
Note that ADC0L is not available on the ADuC848.

0 1 1 Continuous Conversion. In continuous conversion mode, the ADC data registers are

regularly updated at the selected update rate (see the Sinc Filter SFR Bit Designations
in Table 28).

1 0 0 Internal Zero-Scale Calibration. Internal short automatically connected to the

enabled ADC input(s).

1 0 1 Internal Full-Scale Calibration. Internal or external REFIN± or REFIN2± V

REF

(as

determined by XREF bits in ADC0CON2 and/or AXREF (ADuC845 only) in ADC1CON
(ADuC845 only) is automatically connected to the enabled ADC input(s) for this
calibration.

1 1 0 System Zero-Scale Calibration. User should connect system zero-scale input to the

enabled ADC input(s) as selected by CH3CH0 and ACH3ACH0 bits in the
ADC0CON2 and ADC1CON (ADuC845 only) registers.

2, 1, 0

MD2, MD1, MD0

1 1 1 System Full-Scale Calibration. User should connect system full-scale input to the

enabled ADC input(s) as selected by CH3CH0 and ACH3ACH0 bits in the
ADC0CON2 and ADC1CON (ADuC845 only) registers.

ADuC845/ADuC847/ADuC848

Rev. A | Page 42 of 108

Notes on the ADCMODE Register

· Any change to the MD bits immediately resets both ADCs

(auxiliary ADC only applicable to the ADuC845). A write
to the MD2MD0 bits with no change in contents is also
treated as a reset. (See the exception to this in the third
note of this section.)

· If ADC0CON is written when ADC0EN = 1, or if

ADC0EN is changed from 0 to 1, both ADCs are also
immediately reset. In other words, the primary ADC is
given priority over the auxiliary ADC and any change
requested on the primary ADC is immediately responded
to. Only applicable to the ADuC845.

· On the other hand, if ADC1CON is written to or if

ADC1EN is changed from 0 to 1, only the auxiliary ADC is
reset. For example, if the primary ADC is continuously
converting when the auxiliary ADC change or enable
occurs, the primary ADC continues undisturbed. Rather
than allow the auxiliary ADC to operate with a phase
difference from the primary ADC, the auxiliary ADC falls
into step with the outputs of the primary ADC. The result
is that the first conversion time for the auxiliary ADC is
delayed by up to three outputs while the auxiliary ADC
update rate is synchronized to the primary ADC. Only
applicable to ADuC845. If the ADC1CON write occurs
after the primary ADC has completed its operation, the
auxiliary ADC can respond immediately without having to
fall into step with the primary ADCs output cycle.

· If the parts are powered down via the PD bit in the PCON

register, the current ADCMODE bits are preserved, that is,
they are not reset to default state. Upon a subsequent
resumption of normal operating mode, the ADCs restarts
the selected operation defined by the ADCMODE register.

· Once ADCMODE has been written with a calibration

mode, the RDY0/1 (ADuC845 only) bits (ADCSTAT) are
reset and the calibration commences. On completion, the
appropriate calibration registers are written, the relevant
bits in ADCSTAT are written, and the MD2MD0 bits are
reset to 000b to indicate that the ADC is back in power-
down mode.

· Any calibration request of the auxiliary ADC while the

temperature sensor is selected fails to complete. Although
the RDY1 bit is set at the end of the calibration cycle, no
update of the calibration SFRs takes place, and the ERR1
bit is set. ADuC845 only.

· Calibrations performed at maximum SF (see Table 28)

value (slowest ADC throughput rate) help to ensure
optimum calibration.

· The duration of a calibration cycle is 2/Fadc for chop-on

mode and 4/Fadc for chop-off mode.

ADuC845/ADuC847/ADuC848

Rev. A | Page 43 of 108

ADC0CON1 (PRIMARY ADC CONTROL REGISTER)

ADC0CON1 is used to configure the primary ADC for buffer, unipolar, or bipolar coding, and ADC range configuration.

SFR Address:

D2H

Power-On Default:

07H

Bit Addressable:

Table 25. ADC0CON1 SFR Bit Designations

Bit No.

Name

Description

Buffer Configuration Bits.
BUF1 BUF0

Buffer

Configuration

ADC0+ and ADC0- are buffered

0 1

Reserved

Buffer Bypass

7, 6

BUF1, BUF0

1 1

Reserved

UNI

Primary ADC Unipolar Bit.
Set by the user to enable unipolar coding; zero differential input results in 000000H output.
Cleared by the user to enable bipolar coding; zero differential input results in 800000H output.

Not Implemented. Write Don't Care.

Not Implemented. Write Don't Care.
Primary ADC Range Bits. Written by the user to select the primary ADC input range as follows:
RN2

RN1

RN0

Selected primary ADC input range (V

REF

= 2.5 V)

±20 mV (0 mV20 mV in unipolar mode)

±40 mV (0 mV40 mV in unipolar mode)

±80 mV (0 mV80 mV in unipolar mode)

±160 mV (0 mV160 mV in unipolar mode)

±320 mV (0 mV320 mV in unipolar mode)

±640 mV (0 mV640 mV in unipolar mode)

±1.28 V (0 V1.28 V in unipolar mode)

2, 1, 0

RN2, RN1, RN0

±2.56 V (0 V2.56 V in unipolar mode)

ADuC845/ADuC847/ADuC848

Rev. A | Page 44 of 108

ADC0CON2 (PRIMARY ADC CHANNEL SELECT REGISTER)

ADC0CON2 is used to select a reference source and channel for the primary ADC.

SFR Address:

E6H

Power-On Default:

00H

Bit Addressable:

Table 26. ADC0CON2 SFR Bit Designations

Bit No.

Name

Description

Primary ADC External Reference Select Bit.
Set by the user to enable the primary ADC to use the external reference via REFIN± or REFIN2±.
Cleared by the user to enable the primary ADC to use the internal band gap reference (V

REF

= 1.25 V).

XREF1 XREF0

0 0 Internal

1.25

Reference.

0 1 REFIN±

Selected.

1 0 REFIN2±

(AIN3/AIN4)

Selected.

7, 6

XREF1, XREF0

1 1 Reserved.

Not Implemented. Write Don't Care.

Not Implemented. Write Don't Care.
Primary ADC Channel Select Bits. Written by the user to select the primary ADC channel as follows:
CH3

CH2

CH1

CH0

Selected Primary ADC Input Channel.

0 0 0 0 AIN1AINCOM
0 0 0 1 AIN2AINCOM
0 0 1 0 AIN3AINCOM
0 0 1 1 AIN4AINCOM
0 1 0 0 AIN5AINCOM
0 1 0 1 AIN6AINCOM
0 1 1 0 AIN7AINCOM
0 1 1 1 AIN8AINCOM
1

AIN9AINCOM (CSP package only; not a valid selection on the MQFP package)

AIN10AINCOM (CSP package only; not a valid selection on the MQFP package)

1 0 1 0 AIN1AIN2
1 0 1 1 AIN3AIN4
1 1 0 0 AIN5AIN6
1 1 0 1 AIN7AIN8
1

AIN9AIN10 (CSP package only; not a valid selection on the MQFP package)

3, 2, 1, 0

CH3, CH2, CH1, CH0

1 1 1 1 AINCOMAINCOM

Note that because the reference-detect does not operate on the REFIN2± pair, the REFIN2± pins can go below 1 V.

ADuC845/ADuC847/ADuC848

Rev. A | Page 45 of 108

ADC1CON (AUXILIARY ADC CONTROL REGISTER) (ADuC845 ONLY)

ADC1CON is used to configure the auxiliary ADC for reference, channel selection, and unipolar or bipolar coding. The auxiliary ADC is
available only on the ADuC845.

SFR Address:

D3H

Power-On Default:

00H

Bit Addressable:

Table 27. ADC1CON SFR Bit Designations

Bit No.

Name

Description

Not Implemented. Write Don't Care.

AXREF

Auxiliary (ADuC845 only) ADC External Reference Bit.
Set by the user to enable the auxiliary ADC to use the external reference via REFIN±.
Cleared by the user to enable the auxiliary ADC to use the internal band gap reference.
Auxiliary ADC cannot use the REFIN2± reference inputs.

AUNI

Auxiliary (ADuC845 only) ADC Unipolar Bit.
Set by the user to enable unipolar coding, that is, zero input results in 000000H output.
Cleared by the user to enable bipolar coding, zero input results in 800000H output.

Not Implemented. Write Don't Care.
Auxiliary ADC Channel Select Bits. Written by the user to select the auxiliary ADC channel.
ACH3

ACH2

ACH1

ACH0 Selected Auxiliary ADC Input Range (V

REF

= 2.5 V).

0 0 0 0 AIN1AINCOM
0 0 0 1 AIN2AINCOM
0 0 1 0 AIN3AINCOM
0 0 1 1 AIN4AINCOM
0 1 0 0 AIN5AINCOM
0 1 0 1 AIN6AINCOM
0 1 1 0 AIN7AINCOM
0 1 1 1 AIN8AINCOM
1

AIN9AINCOM (not a valid selection on the MQFP package)

AIN10AINCOM (not a valid selection on the MQFP package)

1 0 1 0 AIN1AIN2
1 0 1 1 AIN3AIN4
1 1 0 0 AIN5AIN6
1 1 0 1 AIN7AIN8
1 1 1 0 Temperature

Sensor

3, 2, 1, 0

ACH3, ACH2, ACH1, ACH0

1 1 1 1 AINCOMAINCOM

Note the following about the temperature sensor:

When the temperature sensor is selected, user code must select the internal reference via the AXREF bit and clear the AUNI bit (ADC1CON.5) to select bipolar coding.
Chop mode must be enabled for correct temperature sensor operation.
The temperature sensor is factory calibrated to yield conversion results 800000H at 0°C (ADC chop on).
A +1°C change in temperature results in a +1 LSB change in the ADC1H register ADC conversion result.
The temperature sensor is not available on the ADuC847 or ADuC848.

ADuC845/ADuC847/ADuC848

Rev. A | Page 46 of 108

SF (ADC SINC FILTER CONTROL REGISTER)

The SF register is used to configure the decimation factor for the ADC, and therefore, has a direct influence on the ADC throughput rate.

SFR Address:

D4H

Power-On Default:

45H

Bit Addressable:

Table 28. Sinc Filter SFR Bit Designations

SF.7 SF.6 SF.5 SF.4 SF.3 SF.2 SF.1 SF.0

0 1 0 0 0 1 0 1

The bits in this register set the decimation factor of the ADC. This has a direct bearing on the throughput rate of the ADC along with the
chop setting. The equations used to determine the ADC throughput rate are

Fadc (Chop On) =

SFword

Ч 8

Ч 32.768 kHz

where SFword is in decimal.

Fadc (Chop Off) =

SFword

Ч 32.768 kHz

where SFword is in decimal.

Table 29. SF SFR Bit Examples

Chop Enabled (ADCMODE.3 = 0)

SF (Decimal)

SF (Hexadecimal)

Fadc (Hz)

Tadc (ms)

Tsettle (ms)

105.3

9.52

19.04

69 45

19.79

50.53

101.1

82 52

16.65

60.06

120.1

255 FF

5.35

186.77

373.54

Chop Disabled (ADCMODE.3 = 1)

SF (Decimal)

SF (Hexadecimal)

Fadc (Hz)

Tadc (ms)

Tsettle (ms)

3 03

1365.3

0.73

2.2

69 45

59.36

16.84

50.52

82 52

49.95

20.02

60.06

255 FF

16.06

62.25

186.8

With chop enabled, if an SF word smaller than 13 is written to this SF register, the filter automatically defaults to 13.

During ADC calibration, the user-programmed value of SF word is used. The SF word does not default to the maximum setting (255) as it
did on previous MicroConverter® products. However, for optimum calibration results, it is recommended that the maximum SF word be set.

ADuC845/ADuC847/ADuC848

Rev. A | Page 48 of 108

NONVOLATILE FLASH/EE MEMORY OVERVIEW

The ADuC845/ADuC847/ADuC848 incorporate Flash/EE
memory technology on-chip to provide the user with nonvolatile,
in-circuit reprogrammable code and data memory space.

Like EEPROM, flash memory can be programmed in-system at
the byte level, although it must first be erased, in page blocks.
Thus, flash memory is often and more correctly referred to as
Flash/EE memory.

EEPROM

TECHNOLOGY

EPROM

TECHNOLOGY

FLASH/EE MEMORY

TECHNOLOGY

IN-CIRCUIT

REPROGRAMMABLE

SPACE EFFICIENT/

DENSITY

04741-0-026

Figure 26. Flash/EE Memory Development

Overall, Flash/EE memory represents a step closer to the ideal
memory device that includes nonvolatility, in-circuit program-
mability, high density, and low cost. The Flash/EE memory
technology incorporated allows the user to update program
code space in-circuit, without needing to replace onetime
programmable (OTP) devices at remote operating nodes.

Flash/EE Memory on the ADuC845, ADuC847, ADuC848

The ADuC845/ADuC847/ADuC848 provide two arrays of
Flash/EE memory for user applications--up to 62 kbytes of
Flash/EE program space and 4 kbytes of Flash/EE data memory
space. Also, 8-kbyte and 32-kbyte program memory options are
available. All examples and references in this datasheet use the
62-kbyte option; however, similar protocols and procedures are
applicable to the 32-kbyte and 8-kbyte options, provided that
the difference in memory size is taken into account.

The 62 kbytes Flash/EE code space are provided on-chip to
facilitate code execution without any external discrete ROM
device requirements. The program memory can be programmed
in-circuit, using the serial download mode provided, using
conventional third party memory programmers, or via any
user-defined protocol in user download (ULOAD) mode.

The 4-kbyte Flash/EE data memory space can be used as a
general-purpose, nonvolatile scratchpad area. User access to this
area is via a group of seven SFRs. This space can be programmed
at a byte level, although it must first be erased in 4-byte pages.

The following sections use the 62-kbyte program space as an
example when referring to program and ULOAD mode. For the
other memory models (32-kbyte and 8-kbyte), the ULOAD
space moves to the top 6 kbytes of the on-chip program memory,
that is, for the 32-kbyte memory model, the ULOAD space is
from 26 kbytes to 32 kbytes. The kernel still resides in the
protected area from 60 kbytes to 62 kbytes. The ULOAD space
resides from 2 kbytes to 8 kbytes on the 8-byte part.

Flash/EE Memory Reliability

The Flash/EE program and data memory arrays on the
ADuC845/ADuC847/ADuC848 are fully qualified for two key
Flash/EE memory characteristics: Flash/EE memory cycling
endurance and Flash/EE memory data retention.

Endurance quantifies the ability of the Flash/EE memory to be
cycled through many program, read, and erase cycles. In real
terms, a single endurance cycle is composed of four
independent, sequential events:

1. Initial page erase sequence

2. Read/verify sequence

3. Byte program sequence

4. Second read/verify sequence

In reliability qualification, every byte in both the program and
data Flash/EE memory is cycled from 00H to FFH until a first
fail is recorded, signifying the endurance limit of the on-chip
Flash/EE memory.

As indicated in the specification table, the ADuC845/ADuC847/
ADuC848 Flash/EE memory endurance qualification has been
carried out in accordance with JEDEC Specification A117 over
the industrial temperature range of 40°C, +25°C, +85°C, and
+125°C. (The CSP package is qualified to +85°C only.) The
results allow the specification of a minimum endurance figure
over supply and temperature of 100,000 cycles, with an endurance
figure of 700,000 cycles being typical of operation at 25°C.

Retention is the ability of the Flash/EE memory to retain its
programmed data over time. Again, the parts have been qualified
in accordance with the formal JEDEC Retention Lifetime
Specification (A117) at a specific junction temperature (T

55°C). As part of this qualification procedure, the Flash/EE
memory is cycled to its specified endurance limit described
previously, before data retention is characterized. This means
that the Flash/EE memory is guaranteed to retain its data for its
full specified retention lifetime every time the Flash/EE memory
is reprogrammed. It should also be noted that retention lifetime,
based on an activation energy of 0.6 eV, derates with T

as shown

in Figure 27.

ADuC845/ADuC847/ADuC848

Rev. A | Page 49 of 108

JUNCTION TEMPERATURE (

°C)

NTION

(Years)

250

200

150

100

110

300

100

ADI SPECIFICATION

100 YEARS MIN.

AT T

= 55

°C

04741-0-028

Figure 27. Flash/EE Memory Data Retention

FLASH/EE PROGRAM MEMORY

The ADuC845/ADuC847/ADuC848 contain a 64-kbyte array of
Flash/EE program memory. The lower 62 kbytes of this program
memory are available to the user for program storage or as
additional NV data memory.

The upper 2 kbytes of this Flash/EE program memory array
contain permanently embedded firmware, allowing in-circuit
serial download, serial debug, and nonintrusive single-pin
emulation. These 2 kbytes of embedded firmware also contain a
power-on configuration routine that downloads factory
calibrated coefficients to the various calibrated peripherals such
as ADC, temperature sensor, current sources, band gap, and
references.

These 2 kbytes of embedded firmware are hidden from the user
code. Attempts to read this space read 0s; therefore, the embedded
firmware appears as NOP instructions to user code.

In normal operating mode (power-on default), the 62 kbytes of
user Flash/EE program memory appear as a single block. This
block is used to store the user code as shown in Figure 28.

EMBEDDED DOWNLOAD/DEBUG KERNEL

PERMANENTLY EMBEDDED FIRMWARE ALLOWS

CODE TO BE DOWNLOADED TO ANY OF THE

62 kBYTES OF ON-CHIP PROGRAM MEMORY.

THE KERNEL PROGRAM APPEARS AS NOP

INSTRUCTIONS TO USER CODE.

62 kBYTES OF FLASH/EE PROGRAM MEMORY

ARE AVAILABLE TO THE USER. ALL OF THIS

SPACE CAN BE PROGRAMMED FROM THE

PERMANENTLY EMBEDDED DOWNLOAD/DEBUG

KERNEL OR IN PARALLEL PROGRAMMING MODE.

USER PROGRAM MEMORY

FFFFH

2kBYTE

F800H

F7FFH

62kBYTE

0000H

04741-0-029

Figure 28. Flash/EE Program Memory Map in Normal Mode

In normal mode, the 62 kbytes of Flash/EE program memory
can be programmed by serial downloading and by parallel
programming.

Serial Downloading (In-Circuit Programming)

The ADuC845/ADuC847/ADuC848 facilitates code download
via the standard UART serial port. The parts enter serial down-
load mode after a reset or a power cycle if the PSEN pin is pulled
low through an external 1 k resistor. Once in serial download
mode, the hidden embedded download kernel executes. This
allows the user to download code to the full 62 kbytes of Flash/EE
program memory while the device is in circuit in its target
application hardware.

A PC serial download executable (WSD.EXE) is provided as
part of the ADuC845/ADuC847/ADuC848 Quick Start
development system. Application Note uC004 fully describes
the serial download protocol that is used by the embedded
download kernel. This application note is available at

www.analog.com/microconverter

Parallel Programming

The parallel programming mode is fully compatible with
conventional third-party flash or EEPROM device programmers.
A block diagram of the external pin configuration required to
support parallel programming is shown in Figure 29. In this
mode, Ports 0 and 2 operate as the external address bus interface,
P3 operates as the external data bus interface, and P1.0 operates
as the write enable strobe. P1.1, P1.2, P1.3, and P1.4 are used as
general configuration ports that configures the device for
various program and erase operations during parallel
programming.

P1.4P1.1

P3.7P3.0

RESET

ADuC845/
ADuC847/
ADuC848

+5V

COMMAND

P1.7P1.5

TIMING

DATA

04741-0-030

ENABLE

GND

P1.0

Figure 29. Flash/EE Memory Parallel Programming

The command words that are assigned to P1.1, P1.2, P1.3, and
P1.4 are described in Table 31.

Table 31. Flash/EE Memory Parallel Programming Modes

Port 1 Pins

P1.4 P1.3 P1.2 P1.1 Programming

Mode

0 0 0 0 Erase Flash/EE Program, Data, and

Security Mode

1 0 1 0 Program

Code

Byte

0 0 1 0 Program

Data

Byte

1 0 1 1 Read

Code

Byte

0 0 1 1 Read

Data

Byte

1 1 0 0 Program

Security

Modes

1 1 0 1 Read/Verify

Security

Modes

All other codes

Redundant

ADuC845/ADuC847/ADuC848

Rev. A | Page 50 of 108

USER DOWNLOAD MODE (ULOAD)

Figure 28 shows that it is possible to use the 62 kbytes of
Flash/EE program memory available to the user as one single
block of memory. In this mode, all the Flash/EE memory is
read-only to user code.

However, most of the Flash/EE program memory can also be
written to during run time simply by entering ULOAD mode.
In ULOAD mode, the lower 56 kbytes of program memory can
be erased and reprogrammed by the user software as shown in
Figure 30. ULOAD mode can be used to upgrade the code in
the field via any user-defined download protocol. By configuring
the SPI port on the ADuC845/ADuC847/ADuC848 as a slave, it
is possible to completely reprogram the 56 kbytes of Flash/EE
program memory in under 5 s (see Application Note uC007,
"User Download Mode" at

www.analog.com/microconverter

Alternatively, ULOAD mode can be used to save data to the
56 kbytes of Flash/EE memory. This can be extremely useful in
data logging applications where the parts can provide up to
60 kbytes of data memory on-chip (4 kbytes of dedicated
Flash/EE data memory also exist).

The upper 6 kbytes of the 62 kbytes of Flash/EE program
memory (8 kbytes on the 32-kbyte parts) are programmable
only via serial download or parallel programming. This means
that this space appears as read-only to user code; therefore, it
cannot be accidentally erased or reprogrammed by erroneous
code execution, making it very suitable to use the 6 kbytes as a
bootloader. A bootload enable option exists in the Windows®
serial downloader (WSD) to "Always RUN from E000H after
Reset." If using a bootloader, this option is recommended to
ensure that the bootloader always executes correct code after
reset.

Programming the Flash/EE program memory via ULOAD
mode is described in the Flash/EE Memory Control SFR section
of ECON and also in Application Note uC007
(www.analog.com/microconverter).

EMBEDDED DOWNLOAD/DEBUG KERNEL

PERMANENTLY EMBEDDED FIRMWARE ALLOWS

CODE TO BE DOWNLOADED TO ANY OF THE

62 kBYTES OF ON-CHIP PROGRAM MEMORY.

THE KERNEL PROGRAM APPEARS AS NOP

INSTRUCTIONS TO USER CODE.

USER BOOTLOADER SPACE

THE USER BOOTLOADER

SPACE CAN BE PROGRAMMED IN

DOWNLOAD/DEBUG MODE VIA THE

KERNEL BUT IS READ ONLY WHEN

EXECUTING USER CODE

USER DOWNLOADER SPACE

EITHER THE DOWNLOAD/DEBUG

KERNEL OR USER CODE (IN

ULOAD MODE) CAN PROGRAM

THIS SPACE

FFFFH

2kBYTE

F800H

F7FFH

6kBYTE

E000H

dFFFH

56kBYTE

0000H

04741-0-031

62 kBYTES

OF USER

CODE

MEMORY

Figure 30. Flash/EE Program Memory Map in ULOAD Mode (62-kbyte Part)

The 32-kbyte memory parts have the user bootload space
starting at 6000H. The memory mapping is shown in Figure 31.

EMBEDDED DOWNLOAD/DEBUG KERNEL

PERMANENTLY EMBEDDED FIRMWARE ALLOWS

CODE TO BE DOWNLOADED TO ANY OF THE

32 kBYTES OF ON-CHIP PROGRAM MEMORY.

THE KERNEL PROGRAM APPEARS AS NOP

INSTRUCTIONS TO USER CODE.

USER BOOTLOADER SPACE

THE USER BOOTLOADER

SPACE CAN BE PROGRAMMED IN

DOWNLOAD/DEBUG MODE VIA THE

KERNEL BUT IS READ ONLY WHEN

EXECUTING USER CODE

USER DOWNLOADER SPACE

EITHER THE DOWNLOAD/DEBUG

KERNEL OR USER CODE (IN ULOAD

MODE) CAN PROGRAM THIS SPACE

NOT AVAILABLE TO USER

FFFFH

2kBYTE

F800H

8000H

8kBYTE

6000H

5FFFH

24kBYTE

0000H

04741-A

-
002

32 kBYTES

OF USER

CODE

MEMORY

Figure 31. Flash/EE Program Memory Map in ULOAD Mode (32-kbyte Part)

ULOAD mode is not available on the 8-kbyte Flash/EE program
memory parts.

Flash/EE Program Memory Security

The ADuC845/ADuC847/ADuC848 facilitate three modes of
Flash/EE program memory security: the lock, secure, and serial
safe modes. These modes can be independently activated,
restricting access to the internal code space. They can be
enabled as part of serial download protocol, as described in
Application Note uC004, or via parallel programming.

Lock Mode

This mode locks the code memory, disabling parallel program-
ming of the program memory. However, reading the memory in
parallel mode and reading the memory via a MOVC command
from external memory are still allowed. This mode is deactivated
by initiating an ERASE CODE AND DATA command in serial
download or parallel programming modes.

Secure Mode

This mode locks the code memory, disabling parallel program-
ming of the program memory. Reading/verifying the memory
in parallel mode and reading the internal memory via a MOVC
command from external memory are also disabled. This mode
is deactivated by initiating an ERASE CODE AND DATA
command in serial download or parallel programming modes.

Serial Safe Mode

This mode disables serial download capability on the device. If
serial safe mode is activated and an attempt is made to reset the
part into serial download mode, that is, RESET asserted (pulled
high) and de-asserted (pulled low) with PSEN low, the part
interprets the serial download reset as a normal reset only. It
therefore does not enter serial download mode, but executes only
a normal reset sequence. Serial safe mode can be disabled only
by initiating an ERASE CODE AND DATA command in
parallel programming mode.

ADuC845/ADuC847/ADuC848

Rev. A | Page 51 of 108

USING FLASH/EE DATA MEMORY

The 4 kbytes of Flash/EE data memory are configured as 1024
pages, each of 4 bytes. As with the other ADuC845/ADuC847/
ADuC848 peripherals, the interface to this memory space is via
a group of registers mapped in the SFR space. A group of four
data registers (EDATA14) holds the 4 bytes of data at each
page. The page is addressed via the EADRH and EADRL
registers. Finally, ECON is an 8-bit control register that can be
written to with one of nine Flash/EE memory access commands
to trigger various read, write, erase, and verify functions. A block
diagram of the SFR interface to the Flash/EE data memory array
is shown in Figure 32.

ECON--Flash/EE Memory Control SFR

Programming either Flash/EE data memory or Flash/EE
program memory is done through the Flash/EE memory
control SFR (ECON). This SFR allows the user to read, write,
erase, or verify the 4 kbytes of Flash/EE data memory or the
56 kbytes of Flash/EE program memory.

BYTE 1

(0000H)

DATA1

BYTE 1

(0004H)

BYTE 1

(0008H)

BYTE 1

(000CH)

BYTE 1

(0FF8H)

BYTE 1

(0FFCH)

BYTE 2

(0001H)

DATA2

BYTE 2

(0005H)

BYTE 2

(0009H)

BYTE 2

(000DH)

BYTE 2

(0FF9H)

BYTE 2

(0FFDH)

BYTE 3

(0002H)

DATA3

BYTE 3

(0006H)

BYTE 3

(000AH)

BYTE 3

(000EH)

BYTE 3

(0FFAH)

BYTE 3

(0FFEH)

BYTE 4

(0003H)

DATA4

BYTE 4

(0007H)

BYTE 4

(000BH)

BYTE 4

(000FH)

BYTE 4

(0FFBH)

(0FFFH)

01H

00H

02H

03H

3FEH

3FFH

ADDRE

ADRH/L)

BYTE
ADDRESSES
ARE GIVEN IN
BRACKETS

04741-0-032

BYTE 4

Figure 32. Flash/EE Data Memory Control and Configuration

Table 32. ECON--Flash/EE Memory Commands

ECON Value

Command Description
(Normal Mode, Power-On Default)

Command Description
(ULOAD Mode)

01H Read

4 bytes in the Flash/EE data memory, addressed by the
page address EADRH/L, are read into EDATA14.

Not implemented. Use the MOVC instruction.

02H Write

Results in 4 bytes in EDATA14 being written to the
Flash/EE data memory, at the page address given by
EADRH (0

EADRH < 0400H). Note that the 4 bytes in the

page being addressed must be pre-erased.

Bytes 0 to 255 of internal XRAM are written to the 256 bytes of
Flash/EE program memory at the page address given by
EADRH/L (0

EADRH/L < E0H).

Note that the 256 bytes in the page being addressed must be
pre-erased.

03H Reserved.

Reserved.

04H Verify

Verifies that the data in EDATA14 is contained in the
page address given by EADRH/L. A subsequent read of
the ECON SFR results in a 0 being read if the verification
is valid, or a nonzero value being read to indicate an
invalid verification.

Not implemented. Use the MOVC and MOVX instructions to
verify the Write in software.

05H Erase Page

4-byte page of Flash/EE data memory address is erased
by the page address EADRH/L.

64-byte page of FLASH/EE program memory addressed by the
byte address EADRH/L is erased. A new page starts when EADRL
is equal to 00H, 80H, or C0H.

06H Erase All

4 kbytes of Flash/EE data memory are erased.

The entire 56 kbytes of ULOAD are erased.

81H ReadByte

The byte in the Flash/EE data memory, addressed by the
byte address EADRH/L, is read into EDATA1 (0

EADRH/L

0FFFH).

Not implemented. Use the MOVC command.

82H WriteByte

The byte in EDATA1 is written into Flash/EE data memory
at the byte address EADRH/L.

The byte in EDATA1 is written into Flash/EE program memory at
the byte address EADRH/L (0 EADRH/L DFFFH).

0FH EXULOAD

Configures the ECON instructions (above) to operate on
Flash/EE data memory.

Enters normal mode, directing subsequent ECON instructions to
operate on the Flash/EE data memory.

F0H ULOAD

Enters ULOAD mode; subsequent ECON instructions
operate on Flash/EE program memory.

Enables the ECON instructions to operate on the Flash/EE
program memory. ULOAD entry mode.

ADuC845/ADuC847/ADuC848

Rev. A | Page 52 of 108

Example: Programming the Flash/EE Data Memory

A user wants to program F3H into the second byte on Page 03H
of the Flash/EE data memory space while preserving the other
3 bytes already in this page. A typical program of the Flash/EE
data array involves

1. Setting EADRH/L with the page address.

2. Writing the data to be programmed to the EDATA14.

3. Writing the ECON SFR with the appropriate command.

Step 1: Set Up the Page Address

Address registers EADRH and EADRL hold the high byte
address and the low byte address of the page to be addressed.
The assembly language to set up the address may appear as

MOV EADRH, #0 ;Set Page Address Pointer
MOV EADRL, #03H

Step 2: Set Up the EDATA Registers

Write the four values to be written into the page into the four
SFRs EDATA14. Unfortunately, the user does not know three
of them. Thus, the user must read the current page and overwrite
the second byte.

MOV ECON, #1

;Read Page into EDATA1-4

MOV EDATA2, #0F3H ;Overwrite Byte 2

Step 3: Program Page

A byte in the Flash/EE array can be programmed only if it has
previously been erased. Specifically, a byte can be programmed
only if it already holds the value FFH. Because of the Flash/EE
architecture, this erasure must happen at a page level; therefore,
a minimum of 4 bytes (1 page) are erased when an erase
command is initiated. Once the page is erased, the user can
program the 4 bytes in-page and then perform a verification of
the data.

MOV ECON, #5

;ERASE Page

MOV ECON, #2

;WRITE Page

MOV ECON, #4

;VERIFY Page

MOV A, ECON

;Check if ECON = 0 (OK!)

Although the 4 kbytes of Flash/EE data memory are factory pre-
erased, that is, byte locations set to FFH, it is good programming
practice to include an ERASEALL routine as part of any
configuration/set-up code running on the parts. An ERASEALL
command consists of writing 06H to the ECON SFR, which
initiates an erase of the 4-kbyte Flash/EE array. This command
coded in 8051 assembly language would appear as

MOV ECON, #06H

;ERASE all Command
;2ms duration

FLASH/EE MEMORY TIMING

Typical program and erase times for the parts are as follows:

Normal Mode (Operating on Flash/EE Data Memory)

Command Bytes

Affected

READPAGE

4 bytes

25 machine cycles

WRITEPAGE

4 bytes

380 µs

VERIFYPAGE

4 bytes

25 machine cycles

ERASEPAGE

4 bytes

2 ms

ERASEALL

4 kbytes

2 ms

READBYTE

1 byte

10 machine cycles

WRITEBYTE

1 byte

200 µs

ULOAD Mode (Operating on Flash/EE Program Memory)

WRITEPAGE

256 bytes

15 ms

ERASEPAGE

64 bytes

2 ms

ERASEALL

56 kbytes

2 ms

WRITEBYTE

1 byte

200 µs

Note that a given mode of operation is initiated as soon as the
command word is written to the ECON SFR. The core micro-
controller operation is idled until the requested program/read
or erase mode is completed. In practice, this means that even
though the Flash/EE memory mode of operation is typically
initiated with a two-machine-cycle MOV instruction (to write
to the ECON SFR), the next instruction is not executed until the
Flash/EE operation is complete. This means that the core cannot
respond to interrupt requests until the Flash/EE operation is
complete, although the core peripheral functions such as counter/
timers continue to count as configured throughout this period.

ADuC845/ADuC847/ADuC848

Rev. A | Page 53 of 108

DAC CIRCUIT INFORMATION

The ADuC845/ADuC847/ADuC848 incorporate a 12-bit,
voltage output DAC on-chip. It has a rail-to-rail voltage output
buffer capable of driving 10 k/100 pF, and has two selectable
ranges, 0 V to V

REF

and 0 V to AV

. It can operate in 12-bit or

8-bit mode. The DAC has a control register, DACCON, and two
data registers, DACH/L. The DAC output can be programmed
to appear at Pin 14 or Pin 13 (AINCOM).

Note that in 12-bit mode, the DAC voltage output is updated as
soon as the DACL data SFR is written; therefore, the DAC data
registers should be updated as DACH first, followed by DACL.
The 12-bit DAC data should be written into DACH/L right-
justified such that DACL contains the lower 8 bits, and the
lower nibble of DACH contains the upper 4 bits.

DACCON Control Register

SFR Address:

FDH

Power-On Default:

00H

Bit Addressable:

Table 33. DACCON--DAC Configuration Commands

Bit No.

Name

Description

Not Implemented. Write Don't Care.

DACPIN

DAC Output Pin Select.
Set to 1 by the user to direct the DAC output to Pin 13 (AINCOM).
Cleared to 0 by the user to direct the DAC output to Pin 14 (DAC).

DAC8

DAC 8-Bit Mode Bit.
Set to 1 by the user to enable 8-bit DAC operation. In this mode, the 8 bits in DACL SFR are routed to the 8 MSBs
of the DAC, and the 4 LSBs of the DAC are set to 0.
Cleared to 0 by the user to enable 12-bit DAC operation. In this mode, the 8 LSBs of the result are routed to
DACL, and the upper 4 MSB bits are routed to the lower 4 bits of DACH.

DACRN

DAC Output Range Bit.
Set to 1 by the user to configure the DAC range of 0 V to AV

Cleared to 0 by the user to configure the DAC range of 0 V to 2.5 V (V

REF

DACCLR

DAC Clear Bit.
Set to 1 by the user to enable normal DAC operation.
Cleared to 0 by the user to reset the DAC data registers DACL/H to 0.

DACEN

DAC Enable Bit.
Set to 1 by the user to enable normal DAC operation.
Cleared to 0 by the user to power down the DAC.

DACH/DACL Data Registers

These DAC data registers are written to by the user to update
the DAC output.

FR Address:

DACL (DAC Data Low Byte)--FBH

DACH (DAC Data High Byte)--FCH
Power-On Default:

00H (Both Registers)

Bit Addressable:

No (Both Registers)

ADuC845/ADuC847/ADuC848

Rev. A | Page 54 of 108

Using the DAC

The on-chip DAC architecture consists of a resistor string DAC
followed by an output buffer amplifier, the functional equivalent
of which is shown in Figure 33.

OUTPUT

BUFFER

HIGH-Z

DISABLE

(FROM MCU)

REF

04741-0-033

Figure 33. Resistor String DAC Functional Equivalent

Features of this architecture include inherent guaranteed
monotonicity and excellent differential linearity. As shown in
Figure 33, the reference source for the DAC is user-selectable in
software. It can be either AV

or V

REF

. In 0 V-to-AV

mode,

the DAC output transfer function spans from 0 V to the voltage
at the AV

pin. In 0 V-to-V

REF

mode, the DAC output transfer

function spans from 0 V to the internal V

REF

(2.5 V). The DAC

output buffer amplifier features a true rail-to-rail output stage
implementation. This means that, unloaded, each output is
capable of swinging to within less than 100 mV of both AV

and ground. Moreover, the DAC's linearity specification (when
driving a 10 k resistive load to ground) is guaranteed through
the full transfer function except Codes 0 to 48 in 0 V-to-V

REF

mode and 0 to 100 and 3950 to 4095 in 0 V-to-V

mode.

Linearity degradation near ground and V

is caused by satura-

tion of the output amplifier; a general representation of its effects
(neglecting offset and gain error) is shown in Figure 34. The
dotted line indicates the ideal transfer function, and the solid
line represents what the transfer function might look like with
endpoint nonlinearities due to saturation of the output amplifier.

Note that Figure 34 represents a transfer function in 0-to-V

mode only. In 0 V-to-V

REF

mode (with V

REF

< V

), the lower

nonlinearity would be similar, but the upper portion of the
transfer function would follow the ideal line to the end, showing
no signs of the high-end endpoint linearity error.

50mV

100mV

50mV

0mV

000H

FFFH

04741-

034

Figure 34. Endpoint Nonlinearities Due to Amplifier Saturation

The endpoint nonlinearities shown in Figure 34 become worse
as a function of output loading. Most data sheet specifications
assume a 10 k resistive load to ground at the DAC output. As
the output is forced to source or sink more current, the nonlinear
regions at the top or bottom, respectively, of Figure 34 become
larger. With larger current demands, this can significantly limit
output voltage swing. Figure 35 and Figure 36 illustrate this
behavior. Note that the upper trace in each of these figures is
valid only for an output range selection of 0 V to AV

. In 0 V-

to-V

REF

mode, DAC loading does not cause high-side voltage

nonlinearities while the reference voltage remains below the
upper trace in the corresponding figure. For example, if AV

3 V and V

REF

= 2.5 V, the high-side voltage is not affected by

loads of less than 5 mA. But around 7 mA, the upper curve in
Figure 36 drops below 2.5 V (V

REF

), indicating that at these

higher currents, the output is not capable of reaching V

REF

SOURCE/SINK CURRENT (mA)

OUTPUT VOLTAGE (V)

DAC LOADED WITH 0000H

DAC LOADED WITH 0FFFH

04741-0-035

Figure 35. Source and Sink Current Capability with V

REF

= AV

= 5 V

ADuC845/ADuC847/ADuC848

Rev. A | Page 55 of 108

SOURCE/SINK CURRENT (mA)

OUTPUT VOLTAGE (V)

DAC LOADED WITH 0000H

DAC LOADED WITH 0FFFH

04741-0-036

Figure 36. Source and Sink Current Capability with V

REF

= AV

= 3 V

For larger loads, the current drive capability may not be sufficient.
To increase the source and sink current capability of the DAC,
an external buffer should be added as shown in Figure 37.

ADuC845/
ADuC847/
ADuC848

DAC

04741-0-037

Figure 37. Buffering the DAC Output

The internal DAC output buffer also features a high impedance
disable function. In the chip's default power-on state, the DAC is
disabled and its output is in a high impedance state (or three-
state) where it remains inactive until enabled in software. This
means that if a zero output is desired during power-on or
power-down transient conditions, a pull-down resistor must be
added to each DAC output. Assuming that this resistor is in
place, the DAC output remains at ground potential whenever
the DAC is disabled.

PULSE-WIDTH MODULATOR (PWM)

The ADuC845/ADuC847/ADuC848 has a highly flexible PWM
offering programmable resolution and an input clock. The
PWM can be configured in six different modes of operation.
Two of these modes allow the PWM to be configured as a -
DAC with up to 16 bits of resolution. A block diagram of the
PWM is shown in Figure 38.

CLOCK

SELECT

PROGRAMMABLE

DIVIDER

COMPARE

MODE

PWM0H/L

PWM1H/L

12.583MHz (F

VCO)

32.768kHz/15

32.768kHz (F

XTAL)

EXTERNAL CLOCK ON P2.7

P2.5
P2.6

16-BIT PWM COUNTER

04741-

038

Figure 38. PWM Block Diagram

The PWM uses control SFR, PWMCON, and four data SFRs:
PWM0H, PWM0L, PWM1H, and PWM1L.

PWMCON (as described in Table 34) controls the different
modes of operation of the PWM as well as the PWM clock
frequency. PWM0H/L and PWM1H/L are the data registers that
determine the duty cycles of the PWM outputs at P2.5 and P2.6.

To use the PWM user software, first write to PWMCON to
select the PWM mode of operation and the PWM input clock.
Writing to PWMCON also resets the PWM counter. In any of
the 16-bit modes of operation (Modes 1, 3, 4, 6), user software
should write to the PWM0L or PWM1L SFRs first. This value is
written to a hidden SFR. Writing to the PWM0H or PWM1H
SFRs updates both the PWMxH and the PWMxL SFRs but does
not change the outputs until the end of the PWM cycle in
progress. The values written to these 16-bit registers are then
used in the next PWM cycle.

ADuC845/ADuC847/ADuC848

Rev. A | Page 56 of 108

PWMCON PWM Control SFR

SFR Address:

AEH

Power-On Default:

00H

Bit Addressable:

Table 34. PWMCON PWM Control SFR

Bit No. Name

Description

Not Implemented. Write Don't Care.
PMW Mode Selection.
PWM2 PWM1 PWM0

0 0 0 Mode

PWM

disabled.

Mode 1:

Single 16-bit output with programmable pulse and cycle time.

0 1 0 Mode

Twin

8-bit

outputs.

0 1 1 Mode

Twin

16-bit

outputs.

Mode 4:

Dual 16-bit pulse density outputs.

1 0 1 Mode

Dual

8-bit

outputs.

Mode 6:

Dual 16-bit pulse density RZ outputs.

6, 5, 4

PWM2, PWM1, PWM0

1 1 1 Mode

PWM

counter

reset with outputs not used.

PWM Clock Source Divider.
PWS1 PWS0

0 0 Selected

clock.

Selected clock divided by 4.

Selected clock divided by 16.

3, 2

PWS1, PWS0

Selected clock divided by 64.

PWM Clock Source Selection.
PWC1 PWC0

0 0 F

XTAL

/15 (2.184 kHz).

0 1 F

XTAL

(32.768 kHz).

External input on P2.7.

1, 0

PWC1, PWC0

1 1 F

VCO

(12.58 MHz).

PWM Pulse Width High Byte (PWM0H)

SFR Address:

B2H

Power-On Default:

00H

Bit Addressable:

Table 35. PWM0H: PWM Pulse Width High Byte

PWM0H.7 PWM0H.6 PWM0H.5 PWM0H.4 PWM0H.3 PWM0H.2 PWM0H.1 PWM0H.0

0 0 0 0 0 0 0 0
R/W R/W R/W R/W R/W R/W R/W R/W

PWM Pulse Width Low Byte (PWM0L)

SFR Address:

B1H

Power-On Default:

00H

Bit Addressable:

Table 36. PWM0L: PWM Pulse Width Low Byte

PWM0L.7 PWM0L.6 PWM0L.5 PWM0L.4 PWM0L.3 PWM0L.2 PWM0L.1 PWM0L.0

0 0 0 0 0 0 0 0
R/W R/W R/W R/W R/W R/W R/W R/W

ADuC845/ADuC847/ADuC848

Rev. A | Page 57 of 108

PWM Cycle Width High Byte (PWM1H)

SFR Address:

B4H

Power-On Default:

00H

Bit Addressable:

Table 37. PWM1H: PWM Cycle Width High Byte

PWM1H.7 PWM1H.6 PWM1H.5 PWM1H.4 PWM1H.3 PWM1H.2 PWM1H.1 PWM1H.0

0 0 0 0 0 0 0 0
R/W R/W R/W R/W R/W R/W R/W R/W

PWM Cycle Width Low Byte (PWM1L)

SFR Address:

B3H

Power-On Default:

00H

Bit Addressable:

Table 38. PWM1L: PWM Cycle Width Low Byte

PWM1L.7 PWM1L.6 PWM1L.5 PWM1L.4 PWM1L.3 PWM1L.2 PWM1L.1 PWM1L.0

0 0 0 0 0 0 0 0

R/W R/W R/W R/W R/W R/W R/W R/W

Mode 0

In Mode 0, the PWM is disabled, allowing P2.5 and P2.6 to be
used as normal digital I/Os.

Mode 1 (Single-Variable Resolution PWM)

In Mode 1, both the pulse length and the cycle time (period) are
programmable in user code, allowing the resolution of the PWM
to be variable. PWM1H/L sets the period of the output waveform.
Reducing PWM1H/L reduces the resolution of the PWM output
but increases the maximum output rate of the PWM. For
example, setting PWM1H/L to 65536 gives a 16-bit PWM with
a maximum output rate of 192 Hz (12.583 MHz/65536). Setting
PWM1H/L to 4096 gives a 12-bit PWM with a maximum
output rate of 3072 Hz (12.583 MHz/4096).

PWM0H/L sets the duty cycle of the PWM output waveform as
shown in Figure 39.

P2.6

PWM COUNTER

PWM1H/L

PWM0H/L

04741-0-039

Figure 39. PWM in Mode 1

Mode 2 (Twin 8-Bit PWM)

In Mode 2, the duty cycle and the resolution of the PWM
outputs are programmable. The maximum resolution of the
PWM output is 8 bits.

PWM1L sets the period for both PWM outputs. Typically, this is
set to 255 (FFH) to give an 8-bit PWM, although it is possible to
reduce this as necessary. A value of 100 could be loaded here to
give a percentage PWM, that is, the PWM is accurate to 1%.

The outputs of the PWM at P2.5 and P2.6 are shown in Figure 40.
As can be seen, the output of PWM0 (P2.5) goes low when the
PWM counter equals PWM0L. The output of PWM1 (P2.6) goes
high when the PWM counter equals PWM1H and goes low
again when the PWM counter equals PWM0H. Setting PWM1H
to 0 ensures that both PWM outputs start simultaneously.

P2.6

P2.5

PWM COUNTER

PWM1H

PWM1L

PWM0H

PWM0L

04741-0-040

Figure 40. PWM Mode 2

ADuC845/ADuC847/ADuC848

Rev. A | Page 58 of 108

Mode 3 (Twin 16-Bit PWM)

In Mode 3, the PWM counter is fixed to count from 0 to 65536,
giving a fixed 16-bit PWM. Operating from the 12.58 MHz core
clock results in a PWM output rate of 192 Hz. The duty cycle of
the PWM outputs at P2.5 and P2.6 are independently
programmable.

As shown in Figure 41, while the PWM counter is less than
PWM0H/L, the output of PWM0 (P2.5) is high. Once the PWM
counter equals PWM0H/L, PWM0 (P2.5) goes low and remains
low until the PWM counter rolls over.

Similarly, while the PWM counter is less than PWM1H/L, the
output of PWM1 (P2.6) is high. Once the PWM counter equals
PWM1H/L, PWM1 (P2.6) goes low and remains low until the
PWM counter rolls over.

In this mode, both PWM outputs are synchronized, that is, once
the PWM counter rolls over to 0, both PWM0 (P2.5) and PWM1
(P2.6) go high.

P2.6

P2.5

PWM COUNTER

PWM1H/L

65536

PWM0H/L

04741-0-041

Figure 41. PWM Mode 3

Mode 4 (Dual NRZ 16-Bit -

DAC)

Mode 4 provides a high speed PWM output similar to that of a
- DAC. Typically, this mode is used with the PWM clock
equal to 12.58 MHz.

In this mode, P1.0 and P1.1 are updated every PWM clock
(80 ns in the case of 12.58 MHz). Over any 65536 cycles (16-bit
PWM), PWM0 (P1.0) is high for PWM0H/L cycles and low for
(65536 PWM0H/L) cycles. Similarly, PWM1 (P1.1) is high for
PWM1H/L cycles and low for (65536 PWM1H/L) cycles.

If PWM1H is set to 4010H (slightly above one-quarter of FS),
typically P1.1 is low for three clocks and high for one clock
(each clock is approximately 80 ns). Over every 65536 clocks,
the PWM compromises for the fact that the output should be
slightly above one-quarter of full scale, by having a high cycle
followed by only two low cycles.

12.583MHz

16-BIT

µs

16-BIT

CARRY OUT AT P2.5

CARRY OUT AT P2.6

PWM0H/L = C000H

PWM1H/L = 4000H

LATCH

04741-

042

µs

Figure 42. PWM Mode 4

For faster DAC outputs (at lower resolution), write 0s to the
LSBs that are not required with a 1 in the LSB position. If, for
example, only 12-bit performance is required, write 0001 to the
4 LSBs. This means that a 12-bit accurate - DAC output can
occur at 3 kHz. Similarly, writing 00000001 to the 8 LSBs gives
an 8-bit accurate - DAC output at 49 kHz.

ADuC845/ADuC847/ADuC848

Rev. A | Page 59 of 108

Mode 5 (Dual 8-Bit PWM)

In Mode 5, the duty cycle and the resolution of the PWM outputs
are individually programmable. The maximum resolution of the
PWM output is 8 bits.

P2.6

P2.5

PWM COUNTERS

PWM1H

PWM1L

PWM0H

PWM0L

04741-0-043

Figure 43. PWM Mode 5

Mode 6 (Dual RZ 16-Bit -

DAC)

Mode 6 provides a high speed PWM output similar to that of a
- DAC. Mode 6 operates very similarly to Mode 4; however,
the key difference is that Mode 6 provides return to zero (RZ)
- DAC output. Mode 4 provides non-return-to-zero -
DAC outputs. RZ mode ensures that any difference in the rise
and fall times does not affect the - DAC INL. However, RZ
mode halves the dynamic range of the - DAC outputs from 0
V- to AV

down to 0 V to AV

/2. For best results, this mode

should be used with a PWM clock divider of 4.

If PWM1H is set to 4010H (slightly above one-quarter of FS),
typically P2.6 is low for three full clocks (3 Ч 80 ns), high for
one-half a clock (40 ns), and then low again for one-half a clock
(40 ns) before repeating itself. Over every 65536 clocks, the
PWM compromises for the fact that the output should be
slightly above one-quarter of full scale by leaving the output
high for two half clocks in four every so often.

The output resolution is set by the PWM1L and PWM1H SFRs
for the P2.5 and P2.6 outputs, respectively. PWM0L and PWM0H
set the duty cycles of the PWM outputs at P2.5 and P2.6,
respectively. Both PWMs have the same clock source and clock
divider.

3.146MHz

16-BIT

318

µs

16-BIT

CARRY OUT AT P2.5

CARRY OUT AT P2.6

PWM0H/L = C000H

PWM1H/L = 4000H

LATCH

0 1

318

µs

0, 3/4, 1/2, 1/4, 0

04741-0-044

Figure 44. PWM Mode 6

Mode 7

In Mode 7, the PWM is disabled, allowing P2.5 and P2.6 to be
used as normal.

ADuC845/ADuC847/ADuC848

Rev. A | Page 60 of 108

ON-CHIP PLL (PLLCON)

The ADuC845/ADuC847/ADuC848 are intended for use with a
32.768 kHz watch crystal. A PLL locks onto a multiple (384) of
this to provide a stable 12.582912 MHz clock for the system.
The core can operate at this frequency or at binary submultiples
of it to allow power saving when maximum core performance is
not required. The default core clock is the PLL clock divided by
8 or 1.572864 MHz. The ADC clocks are also derived from the
PLL clock, with the modulator rate being the same as the crystal
oscillator frequency. The control register for the PLL is called
PLLCON and is described as follows.

The 5 V parts can be set to a maximum core frequency of
12.58 MHz (CD2...0 = 000) while at 3 V, the maximum core
clock rate is 6.29 MHz (CD2...0 = 001). The CD bits should not
be set to 000b on the 3 V parts.

The 3 V parts are limited to a core clock speed of 6.29 MHz
(CD = 1).

PLLCON PLL Control Register

SFR Address:

D7H

Power-On Default:

53H

Bit Addressable:

Table 39. PLLCON PLL Control Register

Bit No.

Name

Description

OSC_PD

Oscillator Power-Down Bit.
If low, the 32 kHz crystal oscillator continues running in power-down mode.
If high, the 32.768 kHz oscillator is powered down.
When this bit is low, the seconds counter continues to count in power-down mode and can interrupt the CPU
to exit power-down. The oscillator is always enabled in normal mode.

LOCK

PLL Lock Bit. This is a read-only bit.
Set automatically at power-on to indicate that the PLL loop is correctly tracking the crystal clock. After power-
down, this bit can be polled to wait for the PLL to lock.
Cleared automatically at power-on to indicate that the PLL is not correctly tracking the crystal clock. This
might be due to the absence of a crystal clock or an external crystal at power-on. In this mode, the PLL output
can be 12.58 MHz ± 20%. After the part wakes up from power-down, user code can poll this bit to wait for the
PLL to lock. If LOCK = 0, the PLL is not locked.

Not Implemented. Write Don't Care.

4 LTEA

EA Status. Read-only bit. Reading this bit returns the state of the external EA pin latched at reset or power-on.

FINT

Fast Interrupt Response Bit.
Set by the user to enable the response to any interrupt to be executed at the fastest core clock frequency.
Cleared by the user to disable the fast interrupt response feature.
CPU (Core Clock) Divider Bits. This number determines the frequency at which the core operates.
CD2

CD1

CD0

Core Clock Frequency (MHz)

0 0 12.582912

6.291456 (Maximum core clock rate allowed on the 3 V parts)

1 0 3.145728

1.572864 (Default core frequency)

0 0 0.786432

0 1 0.393216

1 0 0.196608

2, 1, 0

CD2, CD1, CD0

1 1 0.098304

ADuC845/ADuC847/ADuC848

Rev. A | Page 61 of 108

C SERIAL INTERFACE

The ADuC845/ADuC847/ADuC848 support a fully licensed
I

C serial interface. The I

C interface is implemented as a full

hardware slave and software master. SDATA (Pin 27 on the
MQFP package and Pin 29 on the CSP package) is the data I/O
pin. SCLK (Pin 26 on the MQFP package and Pin 28 on the CSP
package) is the serial interface clock for the SPI interface. The
I

C interface on the parts is fully independent of all other pin/

function multiplexing. The I

C interface incorporated on the

ADuC845/ADuC847/ADuC848 also includes a second address
register (I2CADD1) at SFR Address F2H with a default power-
on value of 7FH. The I

C interface is always available to the user

and is not multiplexed with any other I/O functionality on the
chip. This means that the I

C and SPI interfaces can be used at

the same time.

Note that when using the I

C and SPI interfaces simultaneously,

they both use the same interrupt routine (Vector Address 3BH).
When an interrupt occurs from one of these, it is necessary to
interrogate each interface to see which one has triggered the ISR
request.

The four SFRs are used to control the I

C interface are

described next.

I2CCON--I

C Control Register

SFR Address:

E8H

Power-On Default:

00H

Bit Addressable:

Yes

Table 40. I2CCON SFR Bit Designations

Bit No.

Name

Description

7 MDO

C Software Master Data Output Bit (master mode only).

This data bit is used to implement a master I

C transmitter interface in software. Data written to this bit is output on

the SDATA pin if the data output enable bit (MDE) is set.

6 MDE

C Software Output Enable Bit (master mode only).

Set by the user to enable the SDATA pin as an output (Tx).
Cleared by the user to enable the SDATA pin as an input (Rx).

5 MCO

C Software Master Clock Output Bit (master mode only).

This bit is used to implement the SCLK for a master I

C transmitter in software. Data written to this bit is output on

the SCLK pin.

4 MDI

C Software Master Data Input Bit (master mode only).

This data bit is used to implement a master I

C receiver interface in software. Data on the SDATA pin is latched into

this bit on an SCLK transition if the data output enable (MDE) bit is 0.

3 I2CM

C Master/Slave Mode Bit.

Set by the user to enable I

C software master mode.

Cleared by the user to enable I

C hardware slave mode.

2 I2CRS

C Reset Bit (slave mode only).

Set by the user to reset the I

C interface.

Cleared by the user code for normal I

C operation.

1 I2CTX

C Direction Transfer Bit (slave mode only).

Set by the MicroConverter if the I

C interface is transmitting.

Cleared by the MicroConverter if the I

C interface is receiving.

0 I2CI

C Interrupt Bit (slave mode only).

Set by the MicroConverter after a byte has been transmitted or received.
Cleared by the MicroConverter when the user code reads the I2CDAT SFR. I2CI should not be cleared by user code.

ADuC845/ADuC847/ADuC848

Rev. A | Page 62 of 108

I2CADD--I

C Address Register 1

Function:

Holds one of the I

C peripheral addresses for the part. It may be overwritten by user code. Application Note

uC001 at

http://www.analog.com/microconverter

describes the format of the I

C standard 7-bit address.

SFR Address:

9BH

Power-On Default:

55H

Bit Addressable:

I2CADD1--I

C Address Register 2

Function:

Same as the I2CADD.

SFR Address:

F2H

Power-On Default:

7FH

Bit Addressable:

I2CDAT--I

C Data Register

Function:

The I2CDAT SFR is written to by user code to transmit data, or read by user code to read data just received by
the I

C interface. Accessing I2CDAT automatically clears any pending I

C interrupt and the I2CI bit in the

I2CCON SFR. User code should access I2CDAT only once per interrupt cycle.

SFR Address:

9AH

Power-On Default:

00H

Bit Addressable:

The main features of the MicroConverter I

C interface are

· Only two bus lines are required: a serial data line (SDATA)

and a serial clock line (SCLOCK).

· An I

C master can communicate with multiple slave

devices. Because each slave device has a unique 7-bit
address, single master/slave relationships can exist at all
times even in a multislave environment.

· The ability to respond to two separate addresses when

operating in slave mode.

· On-chip filtering rejects <50 ns spikes on the SDATA and

the SCLOCK lines to preserve data integrity.

MASTER

SLAVE 1

SLAVE 2

04741-0-045

Figure 45. Typical I

C System

Software Master Mode

The ADuC845/ADuC847/ADuC848 can be used as an I

master device by configuring the I

C peripheral in master mode

and writing software to output the data bit-by-bit. This is
referred to as a software master. Master mode is enabled by
setting the I2CM bit in the I2CCON register.

To transmit data on the SDATA line, MDE must be set to enable
the output driver on the SDATA pin. If MDE is set, the SDATA
pin is pulled high or low depending on whether the MDO bit is
set or cleared. MCO controls the SCLOCK pin and is always
configured as an output in master mode. In master mode, the
SCLOCK pin is pulled high or low depending on the whether
MCO is set or cleared.

To receive data, MDE must be cleared to disable the output
driver on SDATA. Software must provide the clocks by toggling
the MCO bit and reading the SDATA pin via the MDI bit. If
MDE is cleared, MDI can be used to read the SDATA pin. The
value of the SDATA pin is latched into MDI on a rising edge of
SCLOCK. MDI is set if the SDATA pin is high on the last rising
edge of SCLOCK. MDI is cleared if the SDATA pin is low on
the last rising edge of SCLOCK.

Software must control MDO, MCO, and MDE appropriately to
generate the start condition, slave address, acknowledge bits,
data bytes, and stop conditions. These functions are described
in Application Note uC001.

ADuC845/ADuC847/ADuC848

Rev. A | Page 63 of 108

Hardware Slave Mode

After reset, the ADuC845/ADuC847/ADuC848 default to
hardware slave mode. The I

C interface is enabled by clearing

the SPE bit in SPICON. Slave mode is enabled by clearing the
I2CM bit in I2CCON. The parts have a full hardware slave. In
slave mode, the I

C address is stored in the I2CADD register.

Data received or to be transmitted is stored in the I2CDAT
register.

Once enabled in I

C slave mode, the slave controller waits for

a start condition. If the parts detect a valid start condition,
followed by a valid address, followed by the R/W bit, then the
I2CI interrupt bit is automatically set by hardware. The I

peripheral generates a core interrupt only if the user has pre-
configured the I

C interrupt enable bit in the IEIP2 SFR as well

as the global interrupt bit, EA, in the IE SFR. Therefore,

MOV IEIP2, #01h ;Enable

C Interrupt

SETB EA

An autoclear of the I2CI bit is implemented on the parts so that
this bit is cleared automatically upon read or write access to the
I2CDAT SFR.

MOV I2CDAT, A

;I2CI auto-cleared

MOV A, I2CDAT

;I2CI auto-cleared

If for any reason the user tries to clear the interrupt more than
once, that is, access the data SFR more than once per interrupt,
the I

C controller stops. The interface then must be reset by

using the I2CRS bit.

The user can choose to poll the I2CI bit or to enable the
interrupt. In the case of the interrupt, the PC counter vectors to
003BH at the end of each complete byte. For the first byte, when
the user gets to the I2CI ISR, the 7-bit address and the R/W bit
appear in the I2CDAT SFR.

The I2CTX bit contains the R/W bit sent from the master. If
I2CTX is set, the master is ready to receive a byte; therefore the
slave transmits data by writing to the I2CDAT register. If I2CTX
is cleared, the master is ready to transmit a byte; therefore the
slave receives a serial byte. Software can interrogate the state of
I2CTX to determine whether it should write to or read from
I2CDAT.

Once the part has received a valid address, hardware holds
SCLOCK low until the I2CI bit is cleared by software. This
allows the master to wait for the slave to be ready before
transmitting the clocks for the next byte.

The I2CI interrupt bit is set every time a complete data byte is
received or transmitted, provided that it is followed by a valid
ACK. If the byte is followed by a NACK, an interrupt is not
generated.

The part continues to issue interrupts for each complete data
byte transferred until a stop condition is received or the interface
is reset.

When a stop condition is received, the interface resets to a state
in which it is waiting to be addressed (idle). Similarly, if the
interface receives a NACK at the end of a sequence, it also
returns to the default idle state. The I2CRS bit can be used to
reset the I

C interface. This bit can be used to force the interface

back to the default idle state.

ADuC845/ADuC847/ADuC848

Rev. A | Page 64 of 108

SPI SERIAL INTERFACE

The ADuC845/ADuC847/ADuC848 integrate a complete
hardware serial peripheral interface (SPI) interface on-chip. SPI
is an industry-standard synchronous serial interface that allows
8 bits of data to be synchronously transmitted and received
simultaneously, that is, full duplex. Note that the SPI pins are
multiplexed with the Port 2 pins (P2.0, P2.1, P2.2, and P2.3).
These pins have SPI functionality only if SPE is set. Otherwise,
with SPE cleared, standard Port 2 functionality is maintained.
SPI can be configured for master or slave operation and typically
consists of pins SCLOCK, MISO, MOSI, and SS.

SCLOCK (Serial Clock I/O Pin)

Pin 28 (MQFP Package), Pin 30 (CSP Package)

The master clock (SCLOCK) is used to synchronize the data
transmitted and received through the MOSI and MISO data
lines.

A single data bit is transmitted and received in each SCLOCK
period. Therefore, a byte is transmitted/received after eight
SCLOCK periods. The SCLOCK pin is configured as an output
in master mode and as an input in slave mode. In master mode,
the bit rate, polarity, and phase of the clock are controlled by the
CPOL, CPHA, SPR0, and SPR1 bits in the SPICON SFR (see
Table 41). In slave mode, the SPICON register must be configured
with the same phase and polarity (CPHA and CPOL) as the
master. The data is transmitted on one edge of the SCLOCK
signal and sampled on the other.

MISO (Master In, Slave Out Pin)

Pin 30 (MQFP Package), Pin 32 (CSP Package)
The MISO pin is configured as an input line in master mode
and an output line in slave mode. The MISO line on the master
(data in) should be connected to the MISO line in the slave
device (data out). The data is transferred as byte-wide (8-bit)
serial data, MSB first.

MOSI (Master Out, Slave In Pin)

Pin 29 (MQFP Package), Pin31 (CSP Package)

The MOSI pin is configured as an output line in master mode
and an input line in slave mode. The MOSI line on the master
(data out) should be connected to the MOSI line in the slave
device (data in). The data is transferred as byte-wide (8-bit)
serial data, MSB first.

SS (Slave Select Input Pin)

Pin 31 (MQFP Package), Pin 33 (CSP Package)

The SS pin is used only when the ADuC845/ADuC847/
ADuC848 are configured in SPI slave mode. This line is active
low. Data is received or transmitted in slave mode only when
the SS pin is low, allowing the parts to be used in single-master,
multislave SPI configurations. If CPHA = 1, the SS input can be
pulled low permanently. If CPHA = 0, the SS input must be
driven low before the first bit in a byte-wide transmission or
reception and must return high again after the last bit in that
byte-wide transmission or reception. In SPI slave mode, the
logic level on the external SS pin (Pin 31/ Pin 33) can be read
via the SPR0 bit in the SPICON SFR.

The SFR register in Table 41 is used to control the SPI interface.

ADuC845/ADuC847/ADuC848

Rev. A | Page 65 of 108

SPICON--SPI Control Register

SFR Address:

F8H

Power-On Default:

05H

Bit Addressable:

Yes

Table 41. SPICON SFR Bit Designations

Bit No.

Name

Description

ISPI

SPI Interrupt Bit.
Set by the MicroConverter at the end of each SPI transfer.
Cleared directly by user code or indirectly by reading the SPIDAT SFR.

WCOL

Write Collision Error Bit.
Set by the MicroConverter if SPIDAT is written to while an SPI transfer is in progress.
Cleared by user code.

SPE

SPI Interface Enable Bit.
Set by user code to enable SPI functionality.
Cleared by user code to enable standard Port 2 functionality.

SPIM

SPI Master/Slave Mode Select Bit.
Set by user code to enable master mode operation (SCLOCK is an output).
Cleared by user code to enable slave mode operation (SCLOCK is an input).

3 CPOL

Clock Polarity Bit.
Set by user code to enable SCLOCK idle high.
Cleared by user code to enable SCLOCK idle low.

2 CPHA

Clock Phase Select Bit.
Set by user code if the leading SCLOCK edge is to transmit data.
Cleared by user code if the trailing SCLOCK edge is to transmit data.
SPI Bit-Rate Bits.
SPR1

SPR0

Selected Bit Rate

0 0 f

core

0 1 f

core

1 0 f

core

1, 0

SPR1, SPR0

1 1 f

core

/16

The CPOL and CPHA bits should both contain the same values for master and slave devices.

Note that both SPI and I

C use the same ISR (Vector Address 3BH); therefore, when using SPI and I

C simultaneously, it is necessary to

check the interfaces following an interrupt to determine which one caused the interrupt.

SPIDAT: SPI Data Register

SFR Address:

7FH

Power-On Default: 00H
Bit Addressable:

ADuC845/ADuC847/ADuC848

Rev. A | Page 66 of 108

USING THE SPI INTERFACE

Depending on the configuration of the bits in the SPICON
SFR shown in Table 41, the SPI interface transmits or receives
data in a number of possible modes. Figure 46 shows all
possible ADuC845/ADuC847/ADuC848 SPI configurations
and the timing relationships and synchronization among the
signals involved. Also shown in this figure is the SPI interrupt
bit (ISPI) and how it is triggered at the end of each byte-wide
communication.

SCLOCK

(CPOL = 1)

SCLOCK

(CPOL = 0)

(CPHA = 1)

(CPHA = 0)

SAMPLE INPUT

ISPI FLAG

DATA OUTPUT

ISPI FLAG

SAMPLE INPUT

DATA OUTPUT

MSB BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 LSB

04741-0-046

Figure 46. SPI Timing, All Modes

SPI Interface--Master Mode

In master mode, the SCLOCK pin is always an output and
generates a burst of eight clocks whenever user code writes to
the SPIDAT register. The SCLOCK bit rate is determined by
SPR0 and SPR1 in SPICON. Also note that the SS pin is not
used in master mode. If the parts need to assert the SS pin on an
external slave device, a port digital output pin should be used.

In master mode, a byte transmission or reception is initiated by
a byte write to SPIDAT. The hardware automatically generates
eight clock periods via the SCLOCK pin, and the data is
transmitted via MOSI. With each SCLOCK period, a data bit is
also sampled via MISO. After eight clocks, the transmitted byte
is completely transmitted (via MOSI), and the input byte (if
required) is waiting in the input shift register (after being
received via MISO). The ISPI flag is set automatically, and an
interrupt occurs if enabled. The value in the input shift register
is latched into SPIDAT.

SPI Interface--Slave Mode

In slave mode, the SCLOCK is an input. The SS pin must also be
driven low externally during the byte communication. Trans-
mission is also initiated by a write to SPIDAT. In slave mode, a
data bit is transmitted via MISO, and a data bit is received via
MOSI through each input SCLOCK period. After eight clocks,
the transmitted byte is completely transmitted, and the input
byte is waiting in the input shift register. The ISPI flag is set
automatically, and an interrupt occurs, if enabled. The value in
the shift register is latched into SPIDAT only when the trans-
mission/reception of a byte has been completed. The end of
transmission occurs after the eighth clock has been received if
CPHA = 1, or when SS returns high if CPHA = 0.

ADuC845/ADuC847/ADuC848

Rev. A | Page 67 of 108

DUAL DATA POINTERS

The parts incorporate two data pointers. The second data
pointer is a shadow data pointer and is selected via the data
pointer control SFR (DPCON). DPCON features automatic
hardware post-increment and post-decrement as well as an
automatic data pointer toggle.

DPCON--Data Pointer Control SFR

SFR Address:

A7H

Power-On Default:

00H

Bit Addressable:

Table 42. DPCON SFR Bit Designations

Bit No.

Name

Description

----

Not Implemented. Write Don't Care.

DPT

Data Pointer Automatic Toggle Enable.
Cleared by the user to disable autoswapping of the DPTR.
Set in user software to enable automatic toggling of the DPTR after each MOVX or MOVC instruction.
Shadow Data Pointer Mode. These bits enable extra modes of the shadow data pointer operation, allowing
more compact and more efficient code size and execution.

DP1m1

DP1m0

Behavior of the Shadow Data Pointer

0 0 8052

behavior.

DPTR is post-incremented after a MOVX or a MOVC instruction.

DPTR is post-decremented after a MOVX or MOVC instruction.

5, 4

DP1m1, DP1m0

1 1 DPTR LSB is toggled after a MOVX or MOVC instruction. (This instruction can be useful for

moving 8-bit blocks to/from 16-bit devices.)

Main Data Pointer Mode. These bits enable extra modes of the main data pointer operation, allowing more
compact and more efficient code size and execution.

DP0m1

DP0m0

Behavior of the Main Data Pointer

0 0 8052

behavior.

DPTR is post-incremented after a MOVX or a MOVC instruction.

DPTR is post-decremented after a MOVX or MOVC instruction.

3, 2

DP0m1, DP0m0

1 1 DPTR LSB is toggled after a MOVX or MOVC instruction. (This instruction is useful for

moving 8-bit blocks to/from 16-bit devices.)

----

Not Implemented. Write Don't Care.

DPSEL

Data Pointer Select.
Cleared by the user to select the main data pointer. This means that the contents of this 24-bit register are
placed into the DPL, DPH, and DPP SFRs.
Set by the user to select the shadow data pointer. This means that the contents of a separate 24-bit register
appear in the DPL, DPH, and DPP SFRs.

Note the following:

· The Dual Data Pointer section is the only place in which

main and shadow data pointers are distinguished.
Whenever the DPTR is mentioned elsewhere in this data
sheet, active DPTR is implied.

· Only the MOVC/MOVX @DPTR instructions

automatically post-increment and post-decrement the
DPTR. Other MOVC/MOVX instructions, such as MOVC
PC or MOVC @Ri, do not cause the DPTR to automatically
post-increment and post-decrement.

To illustrate the operation of DPCON, the following code copies
256 bytes of code memory at Address D000H into XRAM,
starting from Address 0000H.

MOV DPTR,#0 ;Main DPTR = 0

MOV DPCON,#55H ;Select shadow DPTR

;DPTR1 increment mode

;DPTR0 increment mode

;DPTR auto toggling ON

MOV DPTR,#0D000H ;DPTR = D000H

MOVELOOP: CLR A

MOVC A,@A+DPTR ;Get data

;Post Inc DPTR

;Swap to Main DPTR(Data)

MOVX @DPTR,A ;Put ACC in XRAM

;Increment main DPTR

;Swap Shadow DPTR(Code)

MOV A, DPL

JNZ MOVELOOP

ADuC845/ADuC847/ADuC848

Rev. A | Page 68 of 108

POWER SUPPLY MONITOR

The power supply monitor, once enabled, monitors the DV

and AV

supplies on the parts. It indicates when any of the

supply pins drop below one of four user-selectable voltage trip
points from 2.63 V to 4.63 V. For correct operation of the power
supply monitor function, AV

must be equal to or greater than

2.63 V. Monitor function is controlled via the PSMCON SFR. If
enabled via the IEIP2 SFR, the monitor interrupts the core by
using the PSMI bit in the PSMCON SFR. This bit is not cleared
until the failing power supply returns above the trip point for at
least 250 ms.

The monitor function allows the user to save working registers
to avoid possible data loss due to the low supply condition, and
also ensures that normal code execution does not resume until a

safe supply level is well established. The supply monitor is also
protected against spurious glitches triggering the interrupt
circuit.

Note that the 5 V part has an internal POR trip level of 4.63 V,
which means that there are no usable DV

PSM trip levels on

the 5 V part. The 3 V part has a POR trip level of 2.63 V
following a reset and initialization sequence, allowing all
relevant PSM trip points to be used.

PSMCON--Power Supply Monitor Control Register

SFR Address:

DFH

Power-On Default:

DEH

Bit Addressable:

Table 43. PSMCON SFR Bit Designations

Bit No.

Name

Description

7 CMPD DV

Comparator Bit.

This read-only bit directly reflects the state of the DV

comparator.

Read 1 indicates that the DV

supply is above its selected trip point.

Read 0 indicates that the DV

supply is below its selected trip point.

6 CMPA AV

Comparator Bit.

This read-only bit directly reflects the state of the AV

comparator.

Read 1 indicates that the AV

supply is above its selected trip point.

Read 0 indicates that the AV

supply is below its selected trip point.

PSMI

Power Supply Monitor Interrupt Bit.
Set high by the MicroConverter if either CMPA or CMPD is low, indicating low analog or digital supply. The PSMI
bit can be used to interrupt the processor. Once CMPD and/or CMPA returns (and remains) high, a 250 ms
counter is started. When this counter times out, the PSMI interrupt is cleared. PSMI can also be written by the
user. However, if either comparator output is low, it is not possible for the user to clear PSMI.
DV

Trip Point Selection Bits.

A 5 V part has no valid PSM trip points. If the DV

supply falls below the 4.63 V point, the part resets (POR). For a

3 V part, all relevant PSM trip points are valid. The 3 V POR trip point is 2.63 V (fixed).
These bits select the DV

trip point voltage as follows:

TPD1 TPD0 Selected

Trip Point (V)

0 0 4.63
0 1 3.08
1 0 2.93

4, 3

TPD1, TPD0

1 1 2.63
AV

Trip Point Selection Bits. These bits select the AV

trip point voltage as follows:

TPA1 TPA0 Selected

Trip Point (V)

0 0 4.63
0 1 3.08
1 0 2.93

2, 1

TPA1, TPA0

1 1 2.63

PSMEN

Power Supply Monitor Enable Bit.
Set to 1 by the user to enable the power supply monitor circuit.
Cleared to 0 by the user to disable the power supply monitor circuit.

ADuC845/ADuC847/ADuC848

Rev. A | Page 69 of 108

WATCHDOG TIMER

The watchdog timer generates a device reset or interrupt within a
reasonable amount of time if the ADuC845/ADuC847/
ADuC848 enters an erroneous state, possibly due to a program-
ming error or electrical noise. The watchdog function can be
disabled by clearing the WDE (watchdog enable) bit in the
watchdog control (WDCON) SFR. When enabled, the watchdog
circuit generates a system reset or interrupt (WDS) if the user
program fails to set the WDE bit within a predetermined amount
of time (see the PRE3...0 bits in Table 44). The watchdog timer

is clocked from the 32 kHz external crystal connected between
the XTAL1 and XTAL2 pins. The WDCOM SFR can be written
only by user software if the double write sequence described in
WDWR is initiated on every write access to the WDCON SFR.

WDCON--Watchdog Control Register

SFR Address:

C0H

Power-On Default:

10H

Bit Addressable:

Yes

Table 44. WDCON SFR Bit Designations

Bit No.

Name

Description

Watchdog Timer Prescale Bits.
The watchdog timeout period is given by the equation
t

= (2

PRE

Ч (2

/ f

XTAL

)) (0 PRE 7; f

XTAL

= 32.768 kHz)

PRE3 PRE2 PRE1 PRE0 Timeout

Period

(ms) Action

0 0 0 0 15.6

Reset

interrupt

0 0 0 1 31.2

Reset

interrupt

0 0 1 0 62.5

Reset

interrupt

0 0 1 1 125

Reset

interrupt

0 1 0 0 250

Reset

interrupt

0 1 0 1 500

Reset

interrupt

0 1 1 0 1000

Reset

interrupt

0 1 1 1 2000

Reset

interrupt

1 0 0 0 0.0

Immediate

reset

7, 6, 5, 4

PRE3, PRE2, PRE1, PRE0

PRE30 > 1000b

Reserved. Not a valid selection.

WDIR

Watchdog Interrupt Response Enable Bit.
If this bit is set by the user, the watchdog generates an interrupt response instead of a system reset
when the watchdog timeout period expires. This interrupt is not disabled by the CLR EA instruction,
and it is also a fixed, high priority interrupt. If the watchdog timer is not being used to monitor the
system, it can be used alternatively as a timer. The prescaler is used to set the timeout period in
which an interrupt is generated.

WDS

Watchdog Status Bit.
Set by the watchdog controller to indicate that a watchdog timeout has occurred.
Cleared by writing a 0 or by an external hardware reset. It is not cleared by a watchdog reset.

WDE

Watchdog Enable Bit.
Set by the user to enable the watchdog and clear its counters. If this bit is not set by the user within
the watchdog timeout period, the watchdog timer generates a reset or interrupt, depending on
WDIR.
Cleared under the following conditions: user writes 0; watchdog reset (WDIR = 0); hardware reset;
PSM interrupt.

WDWR

Watchdog Write Enable Bit.
Writing data to the WDCON SFR involves a double instruction sequence. Global interrupts must first
be disabled. The WDWR bit is set with the very next instruction, a write to the WDCON SFR. For
example:

CLR EA ;Disable Interrupts while configuring to WDT
SETB WDWR ;Allow Write to WDCON
MOV WDCON, #72H ;Enable WDT for 2.0s timeout
SETB EA ;Enable Interrupts again (if required)

ADuC845/ADuC847/ADuC848

Rev. A | Page 70 of 108

TIME INTERVAL COUNTER (TIC)

A TIC is provided on-chip for counting longer intervals than
the standard 8051 compatible timers can count. The TIC is
capable of timeout intervals ranging from 1/128 second to 255
hours. Also, this counter is clocked by the external 32.768 kHz
crystal rather than by the core clock, and it can remain active in
power-down mode and time long power-down intervals. This
has obvious applications for remote battery-powered sensors
where regular widely spaced readings are required. Note that
instructions to the TIC SFRs are also clocked at 32.768 kHz, so
sufficient time must be allowed in user code for these instructions
to execute.

Six SFRs are associated with the time interval counter, TIMECON
being its control register. Depending on the configuration of the
IT0 and IT1 bits in TIMECON, the selected time counter register
overflow clocks the interval counter. When this counter is equal
to the time interval value loaded in the INTVAL SFR, the TII bit
(TIMECON.2) is set and generates an interrupt, if enabled. If
the part is in power-down mode, again with TIC interrupt
enabled, the TII bit wakes up the device and resumes code
execution by vectoring directly to the TIC interrupt service
vector address at 0053H. The TIC-related SFRs are described in
Table 45. Note also that the time based SFRs can be written
initially with the current time; the TIC can then be controlled
and accessed by user software. In effect, this facilitates the
implementation of a real-time clock. A basic block diagram of
the TIC is shown in Figure 47.

Because the TIC is clocked directly from a 32 kHz external
crystal on the parts, instructions that access the TIC registers
are also clocked at 32 kHz (not at the core frequency). The user
must ensure that sufficient time is given for these instructions
to execute.

8-BIT

PRESCALER

HUNDREDTHS COUNTER

HTHSEC

SECOND COUNTER

SEC

MINUTE COUNTER

MIN

HOUR COUNTER

HOUR

TIEN

INTERVAL TIMEOUT

TIME INTERVAL COUNTER INTERRUPT

8-BIT

INTERVAL COUNTER

INTVAL SFR

INTERVAL

TIMEBASE

SELECTION

MUX

TCEN

32.768kHz EXTERNAL CRYSTAL

ITS0 ITS1

EQUAL?

04741-0-047

Figure 47. TIC Simplified Block Diagram

ADuC845/ADuC847/ADuC848

Rev. A | Page 71 of 108

TIMECON--TIC Control Register

SFR Address:

A1H

Power-On Default:

00H

Bit Addressable:

Table 45. TIMECON SFR Bit Designations

Bit No.

Name

Description

----

Not Implemented. Write Don't Care.

TFH

Twenty-Four Hour Select Bit.
Set by the user to enable the hour counter to count from 0 to 23.
Cleared by the user to enable the hour counter to count from 0 to 255.

5, 4

ITS1, ITS0

Interval Timebase Selection Bits.
ITS1 ITS0

Interval

Timebase

0 0

1/128

Second

0 1

Seconds

1 0

Minutes

1 1

Hours

ST1

Single Time Interval Bit.
Set by the user to generate a single interval timeout. If set, a timeout clears the TIEN bit.
Cleared by the user to allow the interval counter to be automatically reloaded and start counting again at each
interval timeout.

TII

TIC Interrupt Bit.
Set when the 8-bit interval counter matches the value in the INTVAL SFR.
Cleared by user software.

TIEN

Time Interval Enable Bit.
Set by the user to enable the 8-bit time interval counter.
Cleared by the user to disable the interval counter.

TCEN

Time Clock Enable Bit.
Set by the user to enable the time clock to the time interval counters.
Cleared by the user to disable the clock to the time interval counters and reset the time interval SFRs to the last
value written to them by the user. The time registers (HTHSEC, SEC, MIN, and HOUR) can be written while TCEN is
low.

ADuC845/ADuC847/ADuC848

Rev. A | Page 72 of 108

INTVAL--User Timer Interval Select Register

Function:

User code writes the required time interval to this register. When the 8-bit interval counter is equal to the time interval
value loaded in the INTVAL SFR, the TII bit (TIMECON.2) is set and generates an interrupt, if enabled.

SFR Address:

A6H

Power-On Default:

00H

Bit Addressable:

Valid Value:

0 to 255 decimal

HTHSEC--Hundredths of Seconds Time Register

Function:

This register is incremented in 1/128-second intervals once TCEN in TIMECON is active. The HTHSEC SFR counts
from 0 to 127 before rolling over to increment the SEC time register.

SFR Address:

A2H

Power-On Default:

00H

Bit Addressable:

Valid Value:

0 to 127 decimal

SEC--Seconds Time Register

Function:

This register is incremented in 1-second intervals once TCEN in TIMECON is active. The SEC SFR counts from 0 to 59
before rolling over to increment the MIN time register.

SFR Address:

A3H

Power-On Default:

00H

Bit Addressable:

Valid Value:

0 to 59 decimal

MIN--Minutes Time Register

Function

This register is incremented in 1-minute intervals once TCEN in TIMECON is active. The MIN SFR counts from 0 to 59
before rolling over to increment the HOUR time register.

SFR Address:

A4H

Power-On Default:

00H

Bit Addressable:

Valid Value:

0 to 59 decimal

HOUR--Hours Time Register

Function:

This register is incremented in 1-hour intervals once TCEN in TIMECON is active. The HOUR SFR counts from 0 to 23
before rolling over to 0.

SFR Address:

A5H

Power-On Default:

00H

Bit Addressable:

Valid Value:

0 to 23 decimal

To enable the TIC as a real-time clock, the HOUR, MIN, SEC, and HTHSEC registers can be loaded with the current time. Once the
TCEN bit is high, the TIC starts. To use the TIC as a time interval counter, select the count interval--hundredths of seconds, seconds,
minutes, and hours via the ITS0 and ITS1 bits in the TIMECON SFR. Load the count required into the INTVAL SFR.

Note that INTVAL is only an 8-bit register, so user software must take into account any intervals longer than are possible with 8 bits.
Therefore, to count an interval of 20 seconds, use the following procedure:

MOV TIMECON, #0D0H ;Enable 24Hour mode, count seconds, Clear TCEN.
MOV INTVAL, #14H ;Load INTVAL with required count interval...in this case 14H = 20
MOV TIMECON, #0D3H ;Start TIC counting and enable the 8bit INTVAL counter.

ADuC845/ADuC847/ADuC848

Rev. A | Page 73 of 108

8052 COMPATIBLE ON-CHIP PERIPHERALS

This section gives a brief overview of the various secondary
peripheral circuits that are available to the user on-chip. These
features are mostly 8052 compatible (with a few additional
features) and are controlled via standard 8052 SFR bit definitions.

Parallel I/O

The ADuC845/ADuC847/ADuC848 use four input/output
ports to exchange data with external devices. In addition to
performing general-purpose I/O, some are capable of external
memory operations, while others are multiplexed with alternate
functions for the peripheral functions available on-chip. In
general, when a peripheral is enabled, that pin cannot be used as
a general-purpose I/O pin.

Port 0

Port 0 is an 8-bit open-drain bidirectional I/O port that is
directly controlled via the Port 0 SFR (80H). Port 0 is also the
multiplexed low-order address and data bus during accesses to
external data memory.

Figure 48 shows a typical bit latch and I/O buffer for a Port 0
pin. The bit latch (one bit in the port's SFR) is represented as a
Type D flip-flop, which clocks in a value from the internal bus
in response to a write to latch signal from the CPU. The
Q output of the flip-flop is placed on the internal bus in
response to a read latch signal from the CPU. The level of the
port pin itself is placed on the internal bus in response to a read
pin signal from the CPU. Some instructions that read a port
activate the read latch signal, and others activate the read pin
signal. See the Read-Modify-Write Instructions section for
details.

CONTROL

READ

LATCH

INTERNAL

BUS

WRITE

TO LATCH

READ

PIN

LATCH

DVDD

ADDR/DATA

P0.x

PIN

04741-0-048

Figure 48. Port 0 Bit Latch and I/O Buffer

As shown in Figure 48, the output drivers of Port 0 pins are
switchable to an internal ADDR and ADDR/DATA bus by an
internal control signal for use in external memory accesses.
During external memory accesses, the P0 SFR has 1s written to
it; therefore, all its bit latches become 1. When accessing
external memory, the control signal in Figure 48 goes high,
enabling push-pull operation of the output pin from the internal
address or data bus (ADDR/DATA line). Therefore, no external
pull-ups are required on Port 0 for it to access external memory.

In general-purpose I/O port mode, Port 0 pins that have 1s
written to them via the Port 0 SFR are configured as open-drain
and, therefore, float. In this state, Port 0 pins can be used as high
impedance inputs. This is represented in Figure 48 by the NAND
gate whose output remains high as long as the control signal is
low, thereby disabling the top FET. External pull-up resistors
are, therefore, required when Port 0 pins are used as general-
purpose outputs. Port 0 pins with 0s written to them drive a
logic low output voltage (V

) and are capable of sinking 1.6 mA.

Port 1

Port 1 is also an 8-bit port directly controlled via the P1 SFR
(90H). Port 1 digital output capability is not supported on this
device. Port 1 pins can be configured as digital inputs or analog
inputs. By (power-on) default, these pins are configured as
analog inputs, that is, 1 is written to the corresponding Port 1
register bit. To configure any of these pins as digital inputs, the
user should write a 0 to these port bits to configure the corre-
sponding pin as a high impedance digital input. These pins also
have various secondary functions aside from their analog input
capability, as described in Table 46.

Table 46. Port 1 Alternate Functions

Pin No.

Alternate Function

P1.2

REFIN2+ (second reference input, +'ve)

P1.3

REFIN2- (second reference input, `ve)

P1.6

IEXC1 (200 µA excitation current source)

P1.7

IEXC2 (200 µA excitation current source)

READ

LATCH

INTERNAL

BUS

WRITE

TO LATCH

READ

PIN

LATCH

P1.x

PIN

TO ADC

04741-0-068

Figure 49. Port 1 Bit Latch and I/O Buffer

Port 2

Port 2 is a bidirectional port with internal pull-up resistors
directly controlled via the P2 SFR. Port 2 also emits the middle-
and high-order address bytes during accesses to the 24-bit
external data memory space.

In general-purpose I/O port mode, Port 2 pins that have 1s
written to them are pulled high by the internal pull-ups as
shown in Figure 50 and, in that state, can be used as inputs. As
inputs, Port 2 pins pulled externally low source current because
of the internal pull-up resistors. Port 2 pins with 0s written to
them drive a logic low output voltage (V

) and are capable of

sinking 1.6 mA.

ADuC845/ADuC847/ADuC848

Rev. A | Page 74 of 108

P2.5 and P2.6 can also be used as PWM outputs, while P2.7 can
act as an alternate PWM clock source. When selected as the
PWM outputs, they overwrite anything written to P2.5 or P2.6.

Table 47. Port 2 Alternate Functions

Pin No.

Alternate Function

P2.0

SCLOCK for SPI

P2.1

MOSI for SPI

P2.2

MISO for SPI

P2.3

SS and T2 clock input

P2.4

T2EX alternate control for T2

P2.5 PWM0

output

P2.6 PWM1

output

P2.7 PWMCLK

CONTROL

READ

LATCH

INTERNAL

BUS

WRITE

TO LATCH

READ

PIN

LATCH

ADDR

P2.x

PIN

INTERNAL

PULL-UP

04741-0-069

Figure 50. Port 2 Bit Latch and I/O Buffer

Port 3

Port 3 is a bidirectional port with internal pull-ups directly
controlled via the P3 SFR (B0H). Port 3 pins that have 1s
written to them are pulled high by the internal pull-ups and, in
that state, can be used as inputs. As inputs, Port 3 pins pulled
externally low source current because of the internal pull-ups.

Port 3 pins with 0s written to them drive a logic low output
voltage (V

) and are capable of sinking 4 mA. Port 3 pins also

have various secondary functions as described in Table 48. The
alternate functions of Port 3 pins can be activated only if the
corresponding bit latch in the P3 SFR contains a 1. Otherwise,
the port pin remains at 0.

Table 48. Port 3 Alternate Functions

Pin No.

Alternate Function

P3.0

RxD (UART input pin, or serial data I/O in Mode 0)

P3.1

TxD (UART output pin, or serial clock output in Mode 0)

P3.2

INT0 (External Interrupt 0)

P3.3

INT1 (External Interrupt 1)

P3.4

T0 (Timer/Counter 0 external input)

P3.5

T1 (Timer/Counter 1 external input)

P3.6

WR (external data memory write strobe)

P3.7

RD (external data memory read strobe)

READ

LATCH

INTERNAL

BUS

WRITE

TO LATCH

READ

PIN

LATCH

P3.x

PIN

INTERNAL

PULL-UP

ALTERNATE

OUTPUT

FUNCTION

ALTERNATE

INPUT

FUNCTION

04741-0-071

Figure 51. Port 3 Bit Latch and I/O Buffer

Read-Modify-Write Instructions

Some 8051 instructions read the latch while others read the pin.
The instructions that read the latch rather than the pins are the
ones that read a value, possibly change it, and rewrite it to the
latch. These are called read-modify-write instructions, which
are listed in Table 49. When the destination operand is a port or
a port bit, these instructions read the latch rather than the pin.

Table 49. Read-Modify-Write Instructions

Instruction Description

ANL

Logical AND, for example, ANL P1, A

ORL

Logical OR, for example, ORL P2, A

XRL

Logical EX-OR, for example, XRL P3, A

JBC

Jump if Bit = 1 and clear bit, for example, JBC
P1.1, LABEL

CPL

Complement bit, for example, CPL P3.0

INC

Increment, for example, INC P2

DEC

Decrement, for example, DEC P2

DJNZ

Decrement and jump if not zero, for example,
DJNZ P3, LABEL

MOV PX.Y, C

Move Carry to Bit Y of Port X

CLR PX.Y

Clear Bit Y of Port X

SETB PX.Y

Set Bit Y of Port X

___________________________________________

These instructions read the port byte (all 8 bits), modify the addressed bit,

and write the new byte back to the latch.

Read-modify-write instructions are directed to the latch rather
than to the pin to avoid a possible misinterpretation of the
voltage level of a pin. For example, a port pin might be used to
drive the base of a transistor. When 1 is written to the bit, the
transistor is turned on. If the CPU reads the same port bit at the
pin rather than the latch, it reads the base voltage of the
transistor and interprets it as Logic 0. Reading the latch rather
than the pin returns the correct value of 1.

ADuC845/ADuC847/ADuC848

Rev. A | Page 75 of 108

TIMERS/COUNTERS

The ADuC845/ADuC847/ADuC848 have three 16-bit timer/
counters: Timer 0, Timer 1, and Timer 2. The timer/counter
hardware is included on-chip to relieve the processor core of the
overhead inherent in implementing timer/counter functionality
in software. Each timer/counter consists of two 8-bit registers:
THx and TLx (x = 0, 1, or 2). All three can be configured to
operate either as timers or as event counters.

When functioning as a timer, the TLx register is incremented
every machine cycle. Thus, one can think of it as counting
machine cycles. Because a machine cycle on a single-cycle core
consists of one core clock period, the maximum count rate is
the core clock frequency.

When functioning as a counter, the TLx register is incremented
by a 1-to-0 transition at its corresponding external input pin:
T0, T1, or T2. When the samples show a high in one cycle and a
low in the next cycle, the count is incremented. Because it takes
two machine cycles (two core clock periods) to recognize a
1-to-0 transition, the maximum count rate is half the core clock
frequency.

There are no restrictions on the duty cycle of the external input
signal, but, to ensure that a given level is sampled at least once
before it changes, it must be held for a minimum of one full
machine cycle. User configuration and control of all timer
operating modes is achieved via three SFRs:

TMOD, TCON

--Control and Configuration for Timers 0 and 1.

T2CON

--Control and Configuration for Timer 2.

TMOD--Timer/Counter 0 and 1 Mode Register

SFR Address:

89H

Power-On Default:

00H

Bit Addressable:

Table 50. TMOD SFR Bit Designation

Bit No.

Name

Description

Gate

Timer 1 Gating Control.
Set by software to enable Timer/Counter 1 only while the INT1 pin is high and the TR1 control is set.

Cleared by software to enable Timer 1 whenever the TR1control bit is set.

C/T

Timer 1 Timer or Counter Select Bit.
Set by software to select counter operation (input from T1 pin).
Cleared by software to select the timer operation (input from internal system clock).
Timer 1 Mode Select bits
M1 M0 Description

TH1 operates as an 8-bit timer/counter. TL1 serves as 5-bit prescaler.

16-Bit Timer/Counter. TH1 and TL1 are cascaded; there is no prescaler.

1 0 8-Bit Autoreload Timer/Counter. TH1 holds a value that is to be reloaded into TL1 each time it

overflows.

5, 4

M1, M0

1 1 Timer/Counter

Stopped.

Gate

Timer 0 Gating Control.
Set by software to enable Timer/Counter 0 only while the INT0 pin is high and the TR0 control bit is set.

Cleared by software to enable Timer 0 whenever the TR0 control bit is set.

C/T

Timer 0 Timer or Counter Select Bit.
Set by software to the select counter operation (input from T0 pin).
Cleared by software to the select timer operation (input from internal system clock).
Timer 0 Mode Select Bits
M1 M0 Description
0

TH0 operates as an 8-bit timer/counter. TL0 serves as a 5-bit prescaler.

16-Bit Timer/Counter. TH0 and TL0 are cascaded; there is no prescaler.

1 0 8-Bit Autoreload Timer/Counter. TH0 holds a value that is to be reloaded into TL0 each time it

overflows.

1, 0

M1, M0

TL0 is an 8-bit timer/counter controlled by the standard Timer 0 control bits.
TH0 is an 8-bit timer only, controlled by Timer 1 control bits.

ADuC845/ADuC847/ADuC848

Rev. A | Page 76 of 108

TCON--Timer/Counter 0 and 1 Control Register

SFR Address:

88H

Power-On Default:

00H

Bit Addressable:

Yes

Table 51. TCON SFR Bit Designations

Bit No.

Name

Description

TF1

Timer 1 Overflow Flag.
Set by hardware on a Timer/Counter 1 overflow.
Cleared by hardware when the program counter (PC) vectors to the interrupt service routine.

TR1

Timer 1 Run Control Bit.
Set by the user to turn on Timer/Counter 1.
Cleared by the user to turn off Timer/Counter 1.

TF0

Timer 0 Overflow Flag.
Set by hardware on a Timer/Counter 0 overflow.
Cleared by hardware when the PC vectors to the interrupt service routine.

TR0

Timer 0 Run Control Bit.
Set by the user to turn on Timer/Counter 0.
Cleared by the user to turn off Timer/Counter 0.

3 IE1

External Interrupt 1 (INT1) Flag.

Set by hardware by a falling edge or by a zero level applied to the external interrupt pin, INT1, depending on the
state of Bit IT1.
Cleared by hardware when the PC vectors to the interrupt service routine only if the interrupt was transition-
activated. If level-activated, the external requesting source controls the request flag rather than the on-chip
hardware.

2 IT1

External Interrupt 1 (IE1) Trigger Type.
Set by software to specify edge-sensitive detection, that is, 1-to-0 transition.
Cleared by software to specify level-sensitive detection, that is, zero level.

1 IE0

External Interrupt 0 (INT0) Flag.

Set by hardware by a falling edge or by a zero level being applied to the external interrupt pin, INT0, depending on
the statue of Bit IT0.
Cleared by hardware when the PC vectors to the interrupt service routine only if the interrupt was transition-
activated. If level-activated, the external requesting source controls the request flag rather than the on-chip
hardware.

0 IT0

External Interrupt 0 (IE0) Trigger Type.
Set by software to specify edge-sensitive detection, that is, 1-to-0 transition.
Cleared by software to specify level-sensitive detection, that is, zero level.

___________________________________________

These bits are not used to control Timer/Counters 0 and 1, but are used instead to control and monitor the external INT0 and INT1 interrupt pins.

Timer/Counter 0 and 1 Data Registers

Each timer consists of two 8-bit registers. These can be used as independent registers or combined into a single 16-bit register, depending
on the timers' mode configuration.

TH0 and TL0

--Timer 0 high and low bytes.

SFR Address:

8CH and 8AH, respectively.

Power-On Default:

00H and 00H, respectively.

TH1 and TL1

--Timer 1 high and low bytes.

SFR Address:

8DH and 8BH, respectively.

Power-On Default:

00H and 00H, respectively

ADuC845/ADuC847/ADuC848

Rev. A | Page 77 of 108

Timer/Counter 0 and 1 Operating Modes

This section describes the operating modes for Timer/Counters
0 and 1. Unless otherwise noted, these modes of operation are
the same for both Timer 0 and Timer 1.

Mode 0 (13-Bit Timer/Counter)

Mode 0 configures an 8-bit timer/counter. Figure 52 shows
Mode 0 operation. Note that the divide-by-12 prescaler is not
present on the single-cycle core.

04741-

049

CORE

CLK*

CONTROL

P3.4/T0

GATE

P3.2/INT0

TR0

TF0

TL0

(5 BITS)

TH0

(8 BITS)

INTERRUPT

C/T = 0

C/T = 1

THE CORE CLOCK IS THE OUTPUT OF THE PLL (SEE THE ON-CHIP PLL SECTION)

Figure 52. Timer/Counter 0, Mode 0

In this mode, the timer register is configured as a 13-bit register.
As the count rolls over from all 1s to all 0s, it sets the timer
overflow flag, TF0. TF0 can then be used to request an interrupt.
The counted input is enabled to the timer when TR0 = 1 and
either Gate = 0 or INT0 = 1. Setting Gate = 1 allows the timer to
be controlled by external input INT0 to facilitate pulse-width
measurements. TR0 is a control bit in the special function
register TCON; Gate is in TMOD. The 13-bit register consists of
all 8 bits of TH0 and the lower 5 bits of TL0. The upper 3 bits of
TL0 are indeterminate and should be ignored. Setting the run
flag (TR0) does not clear the registers.

Mode 1 (16-Bit Timer/Counter)

Mode 1 is the same as Mode 0 except that the Mode 1 timer
register runs with all 16 bits. Mode 1 is shown in Figure 53.

CORE

CLK*

CONTROL

P3.4/T0

GATE

TR0

TF0

TL0

(8 BITS)

TH0

(8 BITS)

INTERRUPT

04741-

050

THE CORE CLOCK IS THE OUTPUT OF THE PLL (SEE THE ON-CHIP PLL SECTION)

P3.2/INT

C/T = 0

C/T = 1

Figure 53. Timer/Counter 0, Mode 1

Mode 2 (8-Bit Timer/Counter with Autoreload)

Mode 2 configures the timer register as an 8-bit counter (TL0)
with automatic reload as shown in Figure 54. Overflow from
TL0 not only sets TF0, but also reloads TL0 with the contents of
TH0, which is preset by software. The reload leaves TH0
unchanged.

CONTROL

TF0

TL0

(8 BITS)

INTERRUPT

RELOAD

TH0

(8 BITS)

CORE

CLK*

P3.4/T0

GATE

TR0

04741-

051

THE CORE CLOCK IS THE OUTPUT OF THE PLL (SEE THE ON-CHIP PLL SECTION)

P3.2/INT

C/T = 0

C/T = 1

Figure 54. Timer/Counter 0, Mode 2

Mode 3 (Two 8-Bit Timer/Counters)

Mode 3 has different effects on Timer 0 and Timer 1. Timer 1 in
Mode 3 simply holds its count. The effect is the same as setting
TR1 = 0. Timer 0 in Mode 3 establishes TL0 and TH0 as two
separate counters. This configuration is shown in Figure 55. TL0
uses the Timer 0 control bits C/T, Gate, TR0, INT0, and TF0.
TH0 is locked into a timer function (counting machine cycles)
and takes over the use of TR1 and TF1 from Timer 1. Therefore,
TH0 then controls the Timer 1 interrupt. Mode 3 is provided
for applications requiring an extra 8-bit timer or counter.

When Timer 0 is in Mode 3, Timer 1 can be turned on and off
by switching it out of and into its own Mode 3, or it can still be
used by the serial interface as a baud rate generator. In fact, it
can be used in any application not requiring an interrupt from
Timer 1 itself.

CONTROL

CORE
CLK/12

TF0

TL0

(8 BITS)

INTERRUPT

CORE

CLK*

P3.4/T0

GATE

TR0

TF1

TH0

(8 BITS)

INTERRUPT

CORE

CLK/12

TR1

04741-

052

THE CORE CLOCK IS THE OUTPUT OF THE PLL (SEE THE ON-CHIP PLL SECTION)

P3.2/INT

C/T = 0

C/T = 1

Figure 55. Timer/Counter 0, Mode 3

ADuC845/ADuC847/ADuC848

Rev. A | Page 78 of 108

T2CON--Timer/Counter 2 Control Register

SFR Address:

C8H

Power-On Default:

00H

Bit Addressable:

Yes

Table 52. T2CON SFR Bit Designations

Bit No.

Name

Description

TF2

Timer 2 Overflow Flag.
Set by hardware on a Timer 2 overflow. TF2 cannot be set when either RCLK = 1 or TCLK = 1.
Cleared by user software.

EXF2

Timer 2 External Flag.
Set by hardware when either a capture or reload is caused by a negative transition on T2EX and EXEN2 = 1.
Cleared by user software.

RCLK

Receive Clock Enable Bit.
Set by the user to enable the serial port to use Timer 2 overflow pulses for its receive clock in serial port Modes 1 and 3.
Cleared by the user to enable Timer 1 overflow to be used for the receive clock.

TCLK

Transmit Clock Enable Bit.
Set by the user to enable the serial port to use Timer 2 overflow pulses for its transmit clock in serial port Modes 1 and 3.
Cleared by the user to enable Timer 1 overflow to be used for the transmit clock.

EXEN2

Timer 2 External Enable Flag.
Set by the user to enable a capture or reload to occur as a result of a negative transition on T2EX if Timer 2 is not being
used to clock the serial port.
Cleared by the user for Timer 2 to ignore events at T2EX.

TR2

Timer 2 Start/Stop Control Bit.
Set by the user to start Timer 2.
Cleared by the user to stop Timer 2.

CNT2

Timer 2 Timer or Counter Function Select Bit.
Set by the user to select the counter function (input from external T2 pin).
Cleared by the user to select the timer function (input from on-chip core clock).

CAP2

Timer 2 Capture/Reload Select Bit.
Set by the user to enable captures on negative transitions at T2EX if EXEN2 = 1.
Cleared by the user to enable autoreloads with Timer 2 overflows or negative transitions at T2EX when EXEN2 = 1.
When either RCLK = 1 or TCLK = 1, this bit is ignored and the timer is forced to autoreload on Timer 2 overflow.

Timer/Counter 2 Data Registers

Timer/Counter 2 also has two pairs of 8-bit data registers
associated with it. These are used as both timer data registers
and as timer capture/reload registers.

TH2 and TL2

--Timer 2 data high byte and low byte.

SFR Address:

CDH and CCH respectively.

Power-On Default:

00H and 00H, respectively.

RCAP2H and RCAP2L

--Timer 2 capture/reload byte and low

byte.
SFR Address:

CBH and CAH, respectively.

Power-On Default:

00H and 00H, respectively.

ADuC845/ADuC847/ADuC848

Rev. A | Page 79 of 108

Timer/Counter 2 Operating Modes

The following sections describe the operating modes for
Timer/Counter 2. The operating modes are selected by bits in
the T2CON SFR as shown in Table 53.

Table 53. T2CON Operating Modes

RCLK (or) TCLK

CAP2

TR2

Mode

0 1 16-Bit

Autoreload

1 1 16-Bit

Capture

1 X

Baud

Rate

X X

Off

16-Bit Autoreload Mode

Autoreload mode has two options that are selected by bit
EXEN2 in T2CON. If EXEN2 = 0, when Timer 2 rolls over, it
not only sets TF2 but also causes the Timer 2 registers to be
reloaded with the 16-bit value in registers RCAP2L and
RCAP2H, which are preset by software. If EXEN2 = 1, Timer 2
still performs the above, but with the added feature that a 1-to-0
transition at external input T2EX also triggers the 16-bit reload
and sets EXF2. Autoreload mode is shown in Figure 56.

16-Bit Capture Mode

Capture mode has two options that are selected by Bit EXEN2
in T2CON. If EXEN2 = 0, Timer 2 is a 16-bit timer or counter
that, upon overflowing, sets bit TF2, the Timer 2 overflow bit,
which can be used to generate an interrupt. If EXEN2 = 1,
Timer 2 still performs the above, but a l-to-0 transition on
external input T2EX causes the current value in the Timer 2
registers, TL2 and TH2, to be captured into registers RCAP2L
and RCAP2H, respectively. In addition, the transition at T2EX
causes bit EXF2 in T2CON to be set, and EXF2, like TF2, can
generate an interrupt. Capture mode is shown in Figure 57. The
baud rate generator mode is selected by RCLK = 1 and/or
TCLK = 1.

In either case, if Timer 2 is used to generate the baud rate, the
TF2 interrupt flag does not occur. Therefore, Timer 2 interrupts
do not occur, so they do not have to be disabled. In this mode,
the EXF2 flag can, however, still cause interrupts, which can be
used as a third external interrupt. Baud rate generation is
described as part of the UART serial port operation in the
following section.

CORE

CLK*

PIN

TR2

CONTROL

TL2

(8 BITS)

TH2

(8 BITS)

RELOAD

TF2

EXF2

TIMER

INTERRUPT

EXEN2

CONTROL

TRANSITION

DETECTOR

T2EX

PIN

RCAP2L

RCAP2H

* THE CORE CLOCK IS THE OUTPUT OF THE PLL (SEE THE ON-CHIP PLL SECTION)

04741-0-053

C/ T2 = 0

C/ T2 = 1

Figure 56. Timer/Counter 2, 16-Bit Autoreload Mode

TF2

CORE

CLK*

PIN

TR2

CONTROL

TL2

(8 BITS)

TH2

(8 BITS)

CAPTURE

EXF2

TIMER

INTERRUPT

EXEN2

CONTROL

TRANSITION

DETECTOR

T2EX

PIN

RCAP2L

RCAP2H

THE CORE CLOCK IS THE OUTPUT OF THE PLL (SEE THE ON-CHIP PLL SECTION)

04741-0-054

C/ T2 = 0

C/ T2 = 1

Figure 57. Timer/Counter 2, 16-Bit Capture Mode

ADuC845/ADuC847/ADuC848

Rev. A | Page 80 of 108

UART SERIAL INTERFACE

The serial port is full duplex, meaning that it can transmit and
receive simultaneously. It is also receive buffered, meaning that
it can begin receiving a second byte before a previously received
byte is read from the receive register. However, if the first byte is
still not read by the time reception of the second byte is complete,
the first byte is lost. The physical interface to the serial data
network is via Pins RxD(P3.0) and TxD(P3.1), while the SFR
interface to the UART comprises SBUF and SCON, as described
below.

SBUF SFR

Both the serial port receive and transmit registers are accessed
through the SBUF SFR (SFR address = 99H). Writing to SBUF
loads the transmit register, and reading SBUF accesses a
physically separate receive register.

SCON UART--Serial Port Control Register

SFR Address:

98H

Power-On Default:

00H

Bit Addressable:

Yes

Table 54. SCON SFR Bit Designations

Bit No.

Name

Description

UART Serial Mode Select Bits. These bits select the serial port operating mode as follows:

SM0

SM1

Selected Operating Mode.

Mode 0: Shift register, fixed baud rate (Core_Clk/2).

Mode 1: 8-bit UART, variable baud rate.

Mode 2: 9-bit UART, fixed baud rate (Core_Clk/32) or (Core_Clk/16).

7, 6

SM0, SM1

Mode 3: 9-bit UART, variable baud rate.

SM2

Multiprocessor Communication Enable Bit.
Enables multiprocessor communication in Modes 2 and 3.
In Mode 0, SM2 should be cleared.
In Mode 1, if SM2 is set, RI is not activated if a valid stop bit was not received. If SM2 is cleared, RI is set as soon as
the byte of data is received.
In Modes 2 or 3, if SM2 is set, RI is not activated if the received ninth data bit in RB8 is 0.
If SM2 is cleared, RI is set as soon as the byte of data is received.

REN

Serial Port Receive Enable Bit.
Set by user software to enable serial port reception.

TB8

Serial Port Transmit (Bit 9).
The data loaded into TB8 is the ninth data bit transmitted in Modes 2 and 3. Cleared by user software to disable
serial port reception.

RB8

Serial Port Receiver Bit 9.
The ninth data bit received in Modes 2 and 3 is latched into RB8. For Mode 1, the stop bit is latched into RB8.

Serial Port Transmit Interrupt Flag.
Set by hardware at the end of the eighth bit in Mode 0, or at the beginning of the stop bit in Modes 1, 2, and 3.
TI must be cleared by user software.

Serial Port Receive Interrupt Flag.
Set by hardware at the end of the eighth bit in Mode 0, or halfway through the stop bit in Modes 1, 2, and 3.
RI must be cleared by software.

SBUF--UART Serial Port Data Register

SFR Address:

99H

Power-On Default:

00H

Bit Addressable:

ADuC845/ADuC847/ADuC848

Rev. A | Page 81 of 108

Mode 0 (8-Bit Shift Register Mode)

Mode 0 is selected by clearing both the SM0 and SM1 bits in the
SFR SCON. Serial data enters and exits through RxD. TxD
outputs the shift clock. Eight data bits are transmitted or
received. Transmission is initiated by any instruction that writes
to SBUF. The data is shifted out of the RxD line. The 8 bits are
transmitted with the least significant bit (LSB) first.

Reception is initiated when the receive enable bit (REN) is 1
and the receive interrupt bit (RI) is 0. When RI is cleared, the
data is clocked into the RxD line, and the clock pulses are
output from the TxD line as shown in Figure 58.

RxD

(DATA OUT)

TxD

(SHIFT CLOCK)

DATA BIT 0

DATA BIT 1

DATA BIT 6

DATA BIT 7

04741-0-055

Figure 58. 8-Bit Shift Register Mode

Mode 1 (8-Bit UART, Variable Baud Rate)

Mode 1 is selected by clearing SM0 and setting SM1. Each data
byte (LSB first) is preceded by a start bit (0) and followed by a
stop bit (1). Therefore, 10 bits are transmitted on TxD or are
received on RxD. The baud rate is set by the Timer 1 or Timer 2
overflow rate, or a combination of the two (one for transmission
and the other for reception).

Transmission is initiated by writing to SBUF. The write to SBUF
signal also loads a 1 (stop bit) into the 9th bit position of the
transmit shift register. The data is output bit-by-bit until the
stop bit appears on TxD and the transmit interrupt flag (TI) is
automatically set as shown in Figure 59.

TxD

(SCON.1)

START

BIT

STOP BIT

SET INTERRUPT

I.E., READY FOR MORE DATA

04741-0-056

Figure 59. 8-Bit Variable Baud Rate

Reception is initiated when a 1-to-0 transition is detected on
RxD. Assuming that a valid start bit is detected, character
reception continues. The start bit is skipped and the 8 data bits
are clocked into the serial port shift register. When all 8 bits
have been clocked in, the following events occur:

· The 8 bits in the receive shift register are latched into SBUF.

· The 9th bit (stop bit) is clocked into RB8 in SCON.

· The receiver interrupt flag (RI) is set.

All of the following conditions must be met at the time the final
shift pulse is generated:

· RI = 0

· Either SM2 = 0 or SM2 = 1

· Received stop bit = 1

If any of these conditions is not met, the received frame is
irretrievably lost, and RI is not set.

Mode 2 (9-Bit UART with Fixed Baud Rate)

Mode 2 is selected by setting SM0 and clearing SM1. In this
mode, the UART operates in 9-bit mode with a fixed baud rate.
The baud rate is fixed at Core_Clk/64 by default, although by
setting the SMOD bit in PCON, the frequency can be doubled
to Core_Clk/32. Eleven bits are transmitted or received: a start
bit (0), 8 data bits, a programmable 9th bit, and a stop bit (1).
The 9th bit is most often used as a parity bit, although it can be
used for anything, including a ninth data bit if required.

To transmit, the 8 data bits must be written into SBUF. The
ninth bit must be written to TB8 in SCON. When transmission
is initiated, the 8 data bits (from SBUF) are loaded into the
transmit shift register (LSB first). The contents of TB8 are
loaded into the 9th bit position of the transmit shift register.
The transmission starts at the next valid baud rate clock. The TI
flag is set as soon as the stop bit appears on TxD.

Reception for Mode 2 is similar to that of Mode 1. The 8 data
bytes are input at RxD (LSB first) and loaded onto the receive
shift register. When all 8 bits have been clocked in, the following
events occur:

· The 8 bits in the receive shift register are latched into SBUF.

· The 9th data bit is latched into RB8 in SCON.

· The receiver interrupt flag (RI) is set.

All of the following conditions must be met at the time the final
shift pulse is generated:

· RI = 0

· Either SM2 = 0 or SM2 = 1

· Received stop bit = 1

If any of these conditions is not met, the received frame is
irretrievably lost, and RI is not set.

ADuC845/ADuC847/ADuC848

Rev. A | Page 82 of 108

Mode 3 (9-Bit UART with Variable Baud Rate)

Mode 3 is selected by setting both SM0 and SM1. In this mode,
the 8051 UART serial port operates in 9-bit mode with a variable
baud rate determined by either Timer 1 or Timer 2. The opera-
tion of the 9-bit UART is the same as for Mode 2, but the baud
rate can be varied as for Mode 1.

In all four modes, transmission is initiated by any instruction
that uses SBUF as a destination register. Reception is initiated in
Mode 0 when RI = 0 and REN = 1. Reception is initiated in the
other modes by the incoming start bit if REN = 1.

UART Serial Port Baud Rate Generation

Mode 0 Baud Rate Generation

The baud rate in Mode 0 is fixed:

Mode 0 Baud Rate =

Frequency

Clock

Core

Mode 2 Baud Rate Generation

The baud rate in Mode 2 depends on the value of the SMOD bit
in the PCON SFR. If SMOD = 0, the baud rate is 1/32 of the
core clock. If SMOD = 1, the baud rate is 1/16 of the core clock:

Mode 2 Baud Rate =

SMOD

Ч Core Clock Frequency

Modes 1 and 3 Baud Rate Generation

The baud rates in Modes 1 and 3 are determined by the overflow
rate in Timer 1 or Timer 2, or in both (one for transmit and the
other for receive).

Timer 1 Generated Baud Rates

When Timer 1 is used as the baud rate generator, the baud rates
in Modes 1 and 3 are determined by the Timer 1 overflow rate
and the value of SMOD as follows:

Modes 1 and 3 Baud Rate =

SMOD

Ч Timer 1 Overflow Rate

The Timer 1 interrupt should be disabled in this application.
The timer itself can be configured for either timer or counter
operation, and in any of its three running modes. In the most
typical application, it is configured for timer operation in
autoreload mode (high nibble of TMOD = 0010 binary). In that
case, the baud rate is given by the formula

Modes 1 and 3 Baud Rate =

)

256

(

TH1

Frequency

Clock

Core

SMOD

Timer 2 Generated Baud Rates

Baud rates can also be generated by using Timer 2. Using Timer 2
is similar to using Timer 1 in that the timer must overflow 16
times before a bit is transmitted or received. Because Timer 2
has a 16-bit autoreload mode, a wider range of baud rates is
possible.

Modes 1 and 3 Baud Rate =

Ч Timer 2 Overflow Rate

Therefore, when Timer 2 is used to generate baud rates, the
timer increments every two clock cycles rather than every core
machine cycle as before. It increments six times faster than
Timer 1, and, therefore, baud rates six times faster are possible.
Because Timer 2 has 16-bit autoreload capability, very low baud
rates are still possible.

Timer 2 is selected as the baud rate generator by setting the
TCLK and/or RCLK in T2CON. The baud rates for transmit
and receive can be simultaneously different. Setting RCLK
and/or TCLK puts Timer 2 into its baud rate generator mode as
shown in Figure 60.

In this case, the baud rate is given by the formula

Modes 1 and 3 Baud Rate =

(

)

[

]

(

)

RCAP

Frequency

Clock

Core

65536

CORE

CLK*

PIN

TR2

CONTROL

TL2

(8 BITS)

TH2

(8 BITS)

RELOAD

EXEN2

CONTROL

T2EX

PIN

TRANSITION

DETECTOR

EXF 2

TIMER 2

INTERRUPT

NOTE: AVAILABILITY OF ADDITIONAL

EXTERNAL INTERRUPT

RCAP2L

RCAP2H

TIMER 2

OVERFLOW

RCLK

TCLK

CLOCK

SMOD

TIMER 1

OVERFLOW

C/T2 = 0

C/T2 = 1

THE CORE CLOCK IS THE OUTPUT OF THE PLL (SEE THE ON-CHIP PLL SECTION)

04741-0-057

Figure 60. Timer 2, UART Baud Rates

ADuC845/ADuC847/ADuC848

Rev. A | Page 83 of 108

Timer 3 Generated Baud Rates

The high integer dividers in a UART block mean that high
speed baud rates are not always possible. Also, generating baud
rates requires the exclusive use of a timer, rendering it unusable
for other applications when the UART is required. To address
this problem, the ADuC845/ADuC847/ADuC848 have a
dedicated baud rate timer (Timer 3) specifically for generating
highly accurate baud rates. Timer 3 can be used instead of
Timer 1 or Timer 2 for generating very accurate high speed
UART baud rates including 115200 and 230400. Timer 3 also
allows a much wider range of baud rates to be obtained. In fact,
every desired bit rate from 12 bps to 393216 bps can be
generated to within an error of ±0.8%. Timer 3 also frees up the
other three timers, allowing them to be used for different
applications. A block diagram of Timer 3 is shown in Figure 61.

ч (1 + T3FD/64)

T3 Rx/Tx

CLOCK

CORE

CLK

T3EN

Rx CLOCK

Tx CLOCK

TIMER 1/TIMER 2

Rx CLOCK

FRACTIONAL

DIVIDER

TIMER 1/TIMER 2

Tx CLOCK

ч 16

ч 2

DIV

04741-0-058

Figure 61. Timer 3, UART Baud Rate

Two SFRs (T3CON and T3FD) are used to control Timer 3.
T3CON is the baud rate control SFR, allowing Timer 3 to be
used to set up the UART baud rate, and to set up the binary
divider (DIV).

The appropriate value to write to the DIV2-1-0 bits can be
calculated using the following formula where f

CORE

is defined in

PLLCON SFR. Note that the DIV value must be rounded down.

DIV =

)

(

log

Rate

Baud

Frequency

Clock

Core

T3FD is the fractional divider ratio required to achieve the
required baud rate. The appropriate value for T3FD can be
calculated with the following formula:

T3FD =

Rate

Baud

Frequency

Clock

Core

DIV

-1

Note that T3FD should be rounded to the nearest integer. Once
the values for DIV and T3FD are calculated, the actual baud
rate can be calculated with the following formula:

Actual Baud Rate =

)

(

T3FD

Frequency

Clock

Core

DIV

For example, to get a baud rate of 9600 while operating at a core
clock frequency of 1.5725 MHz, that is, CD = 3,

DIV = log(1572500/(16 Ч 9600))/log2 = 3.35 = 3

Note that the DIV result is rounded down.

T3FD = (2 Ч 1572500)/(2

3-1

Ч 9600) - 64 = 18 = 12H

Therefore, the actual baud rate is 9588 bps, which gives an error
of 0.12%.

The T3CON and T3FD registers are used to control Timer 3.

T3CON Timer 3 Control Register

SFR Address:

9EH

Power-On Default:

00H

Bit Addressable:

Table 55. T3CON SFR Bit Designations

Bit No.

Name

Description

7 T3BAUDEN

T3UARTBAUD

Enable.

Set to enable Timer 3 to generate the baud rate. When set, PCON.7, T2CON.4, and T2CON.5 are
ignored. Cleared to let the baud rate be generated as per a standard 8052.

Not Implemented. Write Don't Care.

2, 1, 0

DIV2, DIV1, DIV0

Binary Divider

DIV2

DIV1

DIV0

Binary Divider 0. See Table 57.

Binary Divider 1. See Table 57.

Binary Divider 2. See Table 57.

Binary Divider 3. See Table 57.

Binary Divider 4. See Table 57.

Binary Divider 5. See Table 57.

Binary Divider 6. See Table 57.

ADuC845/ADuC847/ADuC848

Rev. A | Page 84 of 108

T3FD--Timer 3 Fractional Divider Register

See Table 57 for values.

SFR Address:

9DH

Power-On Default:

00H

Bit Addressable:

Table 56. T3FD SFR Bit Designations

Bit No.

Name

Description

----

Not Implemented. Write Don't Care.

----

Not Implemented. Write Don't Care.

T3FD.5

Timer 3 Fractional Divider Bit 5.

T3FD.4

Timer 3 Fractional Divider Bit 4.

T3FD.3

Timer 3 Fractional Divider Bit 3.

T3FD.2

Timer 3 Fractional Divider Bit 2.

T3FD.1

Timer 3 Fractional Divider Bit 1.

T3FD.0

Timer 3 Fractional Divider Bit 0.

Table 57. Common Baud Rates Using Timer 3 with a 12.58 MHz PLL Clock

Ideal Baud

DIV

T3CON

T3FD

% Error

230400 0

81H 2DH

0.18

115200 0

82H 2DH

0.18

115200 1

81H 2DH

0.18

57600 0

83H 2DH

0.18

57600 1

82H 2DH

0.18

57600 2

81H 2DH

0.18

38400 0

84H 12H

0.12

38400 1

83H 12H

0.12

38400 2

82H 12H

0.12

38400 3

81H 12H

0.12

19200 0

85H 12H

0.12

19200 1

84H 12H

0.12

19200 2

83H 12H

0.12

19200 3

82H 12H

0.12

19200 4

81H 12H

0.12

9600 0

86H

12H

0.12

9600 1

85H

12H

0.12

9600 2

84H

12H

0.12

9600 3

83H

12H

0.12

9600 4

82H

12H

0.12

9600 5

81H

12H

0.12

ADuC845/ADuC847/ADuC848

Rev. A | Page 85 of 108

INTERRUPT SYSTEM

The ADuC845/ADuC847/ADuC848 provide nine interrupt sources with two priority levels. The control and configuration of the
interrupt system is carried out through three interrupt-related SFRs:

Interrupt Enable Register

Interrupt Priority Register

IEIP2

Secondary Interrupt Enable Register

IE--Interrupt Enable Register

SFR Address:

A8H

Power-On Default:

00H

Bit Addressable:

Yes

Table 58. IE SFR Bit Designations

Bit No.

Name

Description

Set by the user to enable all interrupt sources.
Cleared by the user to disable all interrupt sources.

EADC

Set by the user to enable the ADC interrupt.
Cleared by the user to disable the ADC interrupt.

ET2

Set by the user to enable the Timer 2 interrupt.
Cleared by the user to disable the Timer 2 interrupt.

Set by the user to enable the UART serial port interrupt.
Cleared by the user to disable the UART serial port interrupt.

ET1

Set by the user to enable the Timer 1 interrupt.
Cleared by the user to disable the Timer 1 interrupt.

2 EX1

Set by the user to enable External Interrupt 1 (INT0).

Cleared by the user to disable External Interrupt 1 (INT0).

ET0

Set by the user to enable the Timer 0 interrupt.
Cleared by the user to disable the Timer 0 interrupt.

0 EX0

Set by the user to enable External Interrupt 0 (INT0).

Cleared by the user to disable External Interrupt 0 (INT0).

IP--Interrupt Priority Register

SFR Address:

B8H

Power-On Default:

00H

Bit Addressable:

Yes

Table 59. IP SFR Bit Designations

Bit No.

Name

Description

-----

Not Implemented. Write Don't Care.

PADC

ADC Interrupt Priority (1 = High; 0 = Low).

PT2

Timer 2 Interrupt Priority (1 = High; 0 = Low).

UART Serial Port Interrupt Priority (1 = High; 0 = Low).

PT1

Timer 1 Interrupt Priority (1 = High; 0 = Low).

2 PX1

INT0 (External Interrupt 1) priority (1 = High; 0 = Low).

PT0

Timer 0 Interrupt Priority (1 = High; 0 = Low).

0 PX0

INT0 (External Interrupt 0) Priority (1 = High; 0 = Low).

ADuC845/ADuC847/ADuC848

Rev. A | Page 86 of 108

IEIP2--Secondary Interrupt Enable Register

SFR Address:

A9H

Power-On Default:

A0H

Bit Addressable:

Table 60. IEIP2 Bit Designations

Bit No.

Name

Description

----

Not Implemented. Write Don't Care.

PTI

Time Interval Counter Interrupt Priority Setting (1 = High, 0 = Low).

PPSM

Power Supply Monitor Interrupt Priority Setting (1 = High, 0 = Low).

4 PSI

SPI/I

C Interrupt Priority Setting (1 = High, 0 = Low).

----

This bit must contain 0.

ETI

Set by the user to enable the time interval counter interrupt.
Cleared by the user to disable the time interval counter interrupt.

EPSMI

Set by the user to enable the power supply monitor interrupt.
Cleared by the user to disable the power supply monitor interrupt.

ESI

Set by the user to enable the SPI/I

C serial port interrupt.

Cleared by the user to disable the SPI/I

C serial port interrupt.

INTERRUPT PRIORITY

The interrupt enable registers are written by the user to enable
individual interrupt sources; the interrupt priority registers
allow the user to select one of two priority levels for each
interrupt. A high priority interrupt can interrupt the service
routine of a low priority interrupt, and if two interrupts of
different priorities occur at the same time, the higher level
interrupt is serviced first. An interrupt cannot be interrupted by
another interrupt of the same priority level. If two interrupts of
the same priority level occur simultaneously, the polling sequence,
as shown in Table 61, is observed.

Table 61. Priority within Interrupt Level

INTERRUPT VECTORS

When an interrupt occurs, the program counter is pushed onto
the stack, and the corresponding interrupt vector address is
loaded into the program counter. The interrupt vector addresses
are shown in Table 62.

Table 62. Interrupt Vector Addresses

Source Vector

Address

IE0 0003H
TF0

000BH

IE1 0013H
TF1 001BH
RI + TI

0023H

TF2 + EXF2

002BH

RDY0/RDY1 (ADuC845 only)

0033H

ISPI/I2CI 003BH
PSMI 0043H
TII 0053H
WDS 005BH

Source Priority Description

PSMI

1 (Highest)

Power Supply Monitor Interrupt

WDS 2

Watchdog

Timer

Interrupt

IE0

External Interrupt 0

RDY0/RDY1 3

ADC

Interrupt

TF0

Timer/Counter 0 Interrupt

IE1

External Interrupt 1

TF1

Timer/Counter 1 Interrupt

ISPI/I2CI 7

SPI/I

C Interrupt

RI/TI

UART Serial Port Interrupt

TF2/EXF2

Timer/Counter 2 Interrupt

TII

11 (Lowest)

Timer Interval Counter Interrupt

ADuC845/ADuC847/ADuC848

Rev. A | Page 87 of 108

HARDWARE DESIGN CONSIDERATIONS

This section outlines some of the key hardware design
considerations that must be addressed when integrating the
ADuC845/ADuC847/ADuC848 into any hardware system.

EXTERNAL MEMORY INTERFACE

In addition to their internal program and data memories, the
parts can access up to 16 Mbytes of external data memory
(SRAM). No external program memory access is available.

To begin executing code, tie the EA (external access) pin high.
When EA is high (pulled up to V

--see Figure 69), user

program execution starts at Address 0 in the internal 62-kbyte
Flash/EE code space. When executing from internal code space,
accesses to the program space above F7FFH (62 kbytes) are read
as NOP instructions.

Note that a second very important function of the EA pin is
described in the Single-Pin Emulation Mode section under the
Other Hardware Considerations section.

Figure 62 shows a hardware configuration for accessing up to
64 kbytes of external data memory. This interface is standard to
any 8051 compatible MCU.

LATCH

SRAM

A8A15

A0A7

D0D7

(DATA)

ADuC845/
ADuC847/
ADuC848

ALE

04741-0-059

Figure 62. External Data Memory Interface (64-kbyte Address Space)

If access to more than 64 kbytes of RAM is desired, a feature
unique to the MicroConverter allows addressing up to 16 Mbytes
of external RAM simply by adding another latch as shown in
Figure 63.

LATCH

ALE

LATCH

SRAM

A8A15

A0A7

D0D7

(DATA)

A16A23

ADuC845/
ADuC847/
ADuC848

04741-0-060

Figure 63. External Data Memory Interface (16-Mbtye Address Space)

In either implementation, Port 0 (P0) serves as a multiplexed
address/data bus. It emits the low byte of the data pointer (DPL)
as an address, which is latched by ALE prior to data being placed
on the bus by the parts (write operation) or the external data
memory (read operation). Port 2 (P2) provides the data pointer
page byte (DPP) to be latched by ALE, followed by the data
pointer high byte (DPH). If no latch is connected to P2, DPP is
ignored by the SRAM, and the 8051 standard of 64-kbyte external
data memory access is maintained.

The following example shows the code used to write data to
external data memory.

MOV DPP, #10h ;Set addr to 100000h
MOV DPH, #00h
MOV DPL, #00h
MOV A, #'B' ;Write Char `B' (42h)
MOVX @DPTR,A ;Move to DPP:DPH:DPL addr

POWER SUPPLIES

The parts' operational power supply voltage range is 2.7 V to
5.25 V. Although the guaranteed data sheet specifications are
given only for power supplies within 2.7 V to 3.6 V and 4.75 V
to 5.25 V (±5% of the nominal 5 V level), the chip functions
equally well at any power supply level between 2.7 V and 5.25 V.

Separate analog and digital power supply pins (AV

and DV

respectively) allow AV

to be kept relatively free of the noisy

digital signals often present on a system DV

line. In this mode,

the part can also operate with split supplies, that is, using different
voltage supply levels for each supply. For example, the system
can be designed to operate with a DV

voltage level of 3 V and

the AV

level can be at 5 V, or vice versa, if required. A typical

split-supply configuration is shown in Figure 64.

DIGITAL SUPPLY

ANALOG SUPPLY

AGND

DGND

0.1

µF

0.1

µF

ADuC845/
ADuC847/
ADuC848

04741-0-061

Figure 64. External Dual-Supply Connections

(56-Lead CSP Pin Numbering)

ADuC845/ADuC847/ADuC848

Rev. A | Page 88 of 108

As an alternative to providing two separate power supplies,
AV

can be kept quiet by placing a small series resistor and/or

ferrite bead between it and DV

, and then decoupling AV

separately to ground. An example of this configuration is shown
in Figure 65. In this configuration, other analog circuitry (such
as op amps and voltage reference) can be powered from the
AV

supply line as well.

AGND

DGND

DIGITAL SUPPLY

BEAD

1.6

0.1

µF

0.1

µF

ADuC845/
ADuC847/
ADuC848

04741-0-062

Figure 65. External Single-Supply Connections (56-Lead CSP Pin Numbering)

Notice that in both Figure 64 and Figure 65 a large value (10 µF)
reservoir capacitor sits on DV

and a separate 10 µF capacitor

sits on AV

. Also, local decoupling capacitors (0.1 µF) are

located at each V

pin of the chip. As per standard design

practice, be sure to include all of these capacitors and ensure
that the smaller capacitors are closer than the 10 µF capacitors
to each V

pin with lead lengths as short as possible. Connect

the ground terminal of each of these capacitors directly to the
underlying ground plane. Finally, note that, at all times, the
analog and digital ground pins on the part must be referenced
to the same system ground reference point. It is recommended
that the CSP paddle be soldered to ensure mechanical stability
but be floated with respect to system V

s or grounds.

POWER-ON RESET OPERATION

An internal power-on reset (POR) is implemented on the
ADuC845/ADuC847/ADuC848. For DV

below 2.63 V, the

internal POR holds the part in reset. As DV

rises above 2.63 V,

an internal timer times out for typically 128 ms before the part
is released from reset. The user must ensure that the power
supply has at least reached a stable 2.7 V minimum level by this
time. Likewise on power-down, the internal POR holds the part
in reset until the power supply drops below 1 V. Figure 66
illustrates the operation of the internal POR.

128ms TYP

1.0V TYP

128ms TYP

2.63V TYP

1.0V TYP

INTERNAL

CORE RESET

0471-0-063

Figure 66. ADuC845/ADuC847/ADuC848 Internal Power-On Reset Operation

POWER CONSUMPTION

The DV

power supply current consumption is specified in

normal and power-down modes. The AV

power supply

current is specified with the analog peripherals disabled. The
normal mode power consumption represents the current drawn
from DV

by the digital core. The other on-chip peripherals

(such as the watchdog timer and power supply monitor)
consume negligible current and are therefore included with the
normal operating current. The user must add any currents
sourced by the parallel and serial I/O pins, and those sourced by
the DAC to determine the total current needed at the ADuC845/
ADuC847/ADuC848 DV

and AV

supply pins. Also, current

drawn from the DV

supply increases by approximately 5 mA

during Flash/EE erase and program cycles.

POWER-SAVING MODES

Setting the power-down mode bit, PCON.1, in the PCON SFR
described in Table 6, allows the chip to be switched from
normal mode into full power-down mode.

In power-down mode, both the PLL and the clock to the core
are stopped. The on-chip oscillator can be halted or can
continue to oscillate, depending on the state of the oscillator
power-down bit (OSC_PD) in the PLLCON SFR. The TIC,
driven directly from the oscillator, can also be enabled during
power-down. However, all other on-chip peripherals are shut
down. Port pins retain their logic levels in this mode, but the
DAC output goes to a high impedance state (three-state) while
ALE and PSEN outputs are held low. There are five ways to
terminate power-down mode:

· Asserting the RESET Pin

Returns to normal mode. All registers are set to their reset
default value and program execution starts at the reset
vector once the RESET pin is de-asserted.

· Cycling Power

All registers are set to their default state and program exe-
cution starts at the reset vector approximately 128 ms later.

· Time Interval Counter (TIC) Interrupt

If the OSC_PD bit in the PLLCON SFR is clear, the 32 kHz
oscillator remains powered up even in power-down mode.
If the time interval counter (wake-up/RTC timer) is
enabled, a TIC interrupt wakes the part from power-down
mode. The CPU services the TIC interrupt. The RETI at
the end of the TIC ISR returns the core to the next
instruction after that one that enabled power-down.

ADuC845/ADuC847/ADuC848

Rev. A | Page 89 of 108

· SPI Interrupt

If the SERIPD bit in the PCON SFR is set, an SPI interrupt,
if enabled, wakes up the part from power-down mode. The
CPU services the SPI interrupt. The RETI at the end of the
ISR returns the core to the next instruction after the one
that enabled power-down.

· INT0 Interrupt

If the INT0PD bit in the PCON SFR is set, an external
interrupt 0, if enabled, wakes up the part from power-
down. The CPU services the interrupt. The RETI at the end
of the ISR returns the core to the next instruction after the
one that enabled power-down.

Wake-Up from Power-Down Latency

Even with the 32 kHz crystal enabled during power-down, the
PLL takes some time to lock after a wake-up from power-down.
Typically, the PLL takes about 1 ms to lock. During this time,
code executes, but not at the specified frequency. Some opera-
tions, for example, UART communications, require an accurate
clock to achieve the specified 50 Hz/60 Hz rejection from the
ADCs. Therefore, it is advisable to wait until the PLL has locked
before proceeding with normal code execution. The following
code can be used to wait for the PLL to lock:

WAITFORLOCK: MOV A, PLLCON

JNB ACC.6, WAITFORLOCK

If the crystal is powered down during power-down, an additional
delay is associated with the startup of the crystal oscillator
before the PLL can lock. Typically taking about 150 ms, 32 kHz
crystals are inherently slow to oscillate. During this time before
lock, code executes, but the exact frequency of the clock cannot
be guaranteed. For any timing-sensitive operations, it is
recommended to wait for lock by using the lock bit in PLLCON
as shown previously.

An alternative way of saving power in power-down mode
is to slow down the core clock by using the CD bits in the
PLLCON register.

GROUNDING AND BOARD LAYOUT
RECOMMENDATIONS

As with all high resolution data converters, special attention
must be paid to grounding and PC board layout of ADuC845/
ADuC847/ADuC848-based designs in order to achieve
optimum performance from the ADCs and DAC.

Although the parts have separate pins for analog and digital
ground (AGND and DGND), the user must not tie these to
separate ground planes unless the two ground planes are
connected together very close to the part as shown in the
simplified example in Figure 67a. In systems where digital and
analog ground planes are connected together somewhere else
(at the system's power supply, for example), they cannot be
connected again near the part since a ground loop would result.

In these cases, tie the AGND and DGND pins of the part to the
analog ground plane, as shown in Figure 67b. In systems with
only one ground plane, ensure that the digital and analog
components are physically separated onto separate halves of the
board such that digital return currents do not flow near analog
circuitry and vice versa. The parts can then be placed between
the digital and analog sections, as shown in Figure 67c.

In all of these scenarios, and in more complicated real-life
applications, keep in mind the flow of current from the supplies
and back to ground. Make sure that the return paths for all
currents are as close as possible to the paths the currents took to
reach their destinations. For example, do not power components
on the analog side of Figure 67b with DV

since that would

force return currents from DV

to flow through AGND. Also,

try to avoid digital currents flowing under analog circuitry,
which could happen if the user placed a noisy digital chip on
the left half of the board in Figure 67c. Whenever possible,
avoid large discontinuities in the ground plane(s) (such as are
formed by a long trace on the same layer), since they force
return signals to travel a longer path. Make all connections
directly to the ground plane, with little or no trace separating
the pin from its via to ground.

DGND

AGND

PLACE ANALOG

COMPONENTS

HERE

PLACE DIGITAL

COMPONENTS

HERE

GND

PLACE ANALOG

COMPONENTS

HERE

PLACE DIGITAL

COMPONENTS

HERE

DGND

AGND

PLACE ANALOG

COMPONENTS

HERE

PLACE DIGITAL

COMPONENTS

HERE

04741-0-064

Figure 67. System Grounding Schemes

If the user plans to connect fast logic signals (rise/fall time < 5 ns)
to any of the ADuC845/ADuC847/ADuC848's digital inputs,
add a series resistor to each relevant line to keep rise and fall
times longer than 5 ns at the parts input pins. A value of 100
or 200 is usually sufficient to prevent high speed signals from
coupling capacitively into the part and affecting the accuracy of
ADC conversions.

ADuC845/ADuC847/ADuC848

Rev. A | Page 90 of 108

When using the LFCSP package, it is recommended that the
paddle underneath the chip be soldered to the board to provide
maximum mechanical stability. However, it is recommended
that this paddle not be grounded but left floating. All results and
specifications contained in this data sheet are taken or recorded
with the paddle floating.

System Self-Identification

In some hardware designs, it may be an advantage for the
software to be able to identify the host MicroConverter.

The CHIPID SFR is a read-only register located at SFR address
C2H. The upper nibble of this SFR designates the MicroConverter
within the - ADC family. User software can read this SFR to
identify the host MicroConverter and therefore execute slightly
different code if required. The CHIPID SFR reads as follows for
the - ADC family of MicroConverter products. Note that the
ADuC845/ADuC847/ADuC848 are treated as one part as far as
the CHIPID is concerned.

Table 63. CHIPID Values for - MicroConverter Products

Part CHIPID

ADuC816 1xH
ADuC824 0xH
ADuC836 3xH
ADuC834 2xH
ADuC845/ADuC847/ADuC848 AxH

Clock Oscillator

As described earlier, the core clock frequency for the ADuC845/
ADuC847/ADuC848 is generated from an on-chip PLL that
locks onto a multiple (384 times) of 32.768 kHz. The latter is
generated from an internal clock oscillator. To use the internal
clock oscillator, connect a 32.768 kHz parallel resonant crystal
between XTAL1 and XTAL2 as shown in Figure 68.

XTAL2

32.768kHz

12pF

XTAL1

TO INTERNAL PLL

ADuC845/ADuC847/ADuC848

04741-0-065

Figure 68. Crystal Connectivity to ADuC845/ADuC847/ADuC848

As shown in the typical external crystal connection diagram in
Figure 68, two internal 12 pF capacitors are provided on-chip.
These are connected internally, directly to the XTAL1 and XTAL2
pins. The total input capacitance at both pins is detailed in the
Specifications table. Note that the total capacitance required for
a particular crystal must be in accordance with the crystal
manufacturer. However, in most cases, no additional external
capacitance is required above that already supplied on-chip.

OTHER HARDWARE CONSIDERATIONS

In-Circuit Serial Download Access

Nearly all ADuC845/ADuC847/ADuC848 designs can take
advantage of the in-circuit reprogrammability of the chip. This
is accomplished by a connection to the parts" UART, which
requires an external RS-232 chip for level translation if down-
loading code from a PC. Basic configuration of an RS-232
connection is shown in Figure 69 with a simple ADM3202-
based circuit. If users would rather not include an RS-232 chip
on the target board, refer to Application Note uC006,
"A 4-Wire UART-to-PC Interface" available at

www.analog.com/microconverter

, for a simple (and zero-cost-

per-board) method of gaining in-circuit serial download access
to the part.

ADuC845/ADuC847/ADuC848

Rev. A | Page 91 of 108

C1+

V+

C1

C2+

C2

T2OUT

R2IN

GND

T1OUT

R1IN

R1OUT

T1IN

T2IN

R2OUT

ADM3202

RS232 INTERFACE*

STANDARD D-TYPE

SERIAL COMMS

CONNECTOR TO

PC HOST

*EXTERNAL UART TRANSCEIVER INTEGRATED IN SYSTEM OR AS PART
OF AN EXTERNAL DONGLE AS DESCRIBED IN APPLICATION NOTE uC006.

0.1

µF

0.1

µF

0.1

µF

0.1

µF

RESET ACTIVE HIGH.

(NORMALLY OPEN)

2-PIN HEADER FOR

EMULATION ACCESS

(NORMALLY OPEN)

DOWNLOAD/DEBUG

ENABLE JUMPER

(NORMALLY OPEN)

32.768kHz

AGND

REFIN

REFIN+

P1.0/AIN1

P1.1/AIN2

P1.6/I

EXC

1/AIN7

200mA/400mA

EXCITATION

CURRENT

RTD

REF

5.6kV

PSEN

XTAL2

XTAL1

ESET

TxD

DGND

ADuC845/ADuC847/ADuC848

CSP PACKAGE

04741-A

-
001

17 18 19 22 36 51

37 38 50

0.1

µF

Figure 69. UART Connectivity in Typical System

In addition to the basic UART connections, users also need a
way to trigger the chip into download mode. This is accomplished
via a 1 k pull-down resistor that can be jumpered onto the
PSEN pin, as shown in Figure 69. To get the parts into download
mode, connect this jumper and power-cycle the device (or
manually reset the device, if a manual reset button is available),
and it is ready to receive a new program serially. With the
jumper removed, the device powers on in normal mode (and
runs the program) whenever power is cycled or RESET is
toggled. Note that PSEN is normally an output and that it is
sampled as an input only on the falling edge of RESET, that is, at
power-on or upon an external manual reset. Note also that if
any external circuitry unintentionally pulls PSEN low during
power-on or reset events, it could cause the chip to enter

download mode and fail to begin user code execution. To
prevent this, ensure that no external signals are capable of
pulling the PSEN pin low, except for the external PSEN jumper
itself or the method of download entry in use during a reset or
power-cycle condition.

Embedded Serial Port Debugger

From a hardware perspective, entry to serial port debug mode is
identical to the serial download entry sequence described
previously. In fact, both serial download and serial port debug
modes are essentially one mode of operation used in two
different ways.

Note that the serial port debugger is fully contained on the
device, unlike ROM monitor type debuggers, and, therefore, no
external memory is needed to enable in-system debug sessions.

ADuC845/ADuC847/ADuC848

Rev. A | Page 92 of 108

Single-Pin Emulation Mode

Built into the ADuC845/ADuC847/ADuC848 is a dedicated
controller for single-pin in-circuit emulation (ICE). In this mode,
emulation access is gained by connection to a single pin, the EA
pin. Normally on the 8051 standard, this pin is hardwired either
high or low to select execution from internal or external program
memory space. Note that external program memory or execu-
tion from external program memory is not allowed on the
devices. To enable single-pin emulation mode, users need to pull
the EA pin high through a 1 k resistor as shown in Figure 69.
The emulator then connects to the 2-pin header also shown in
Figure 69. To be compatible with the standard connector that
comes with the single-pin emulator available from Accutron
Limited (www.accutron.com), use a 2-pin 0.1-inch pitch
Friction Lock header from Molex (www.molex.com) such as
part number 22-27-2021. Be sure to observe the polarity of this
header. As shown in Figure 69, when the Friction Lock tab is at
the right, the ground pin should be the lower of the two pins
when viewed from the top.

Typical System Configuration

A typical ADuC845/ADuC847/ADuC848 configuration is
shown in Figure 69. Figure 69 also includes connections for a
typical analog measurement application of the parts, namely an
interface to an resistive temperature device (RTD). The
arrangement shown is commonly referred to as a 4-wire RTD
configuration.

Here, the on-chip excitation current sources are enabled to
excite the sensor. The excitation current flows directly through
the RTD generating a voltage across the RTD proportional to its
resistance. This differential voltage is routed directly to one set
of the positive and negative inputs of the ADC (AIN1, AIN2,
respectively in this case). The same current that excited the
RTD also flows through a series resistance, R

REF

, generating a

ratiometric voltage reference, V

REF

. The ratiometric voltage

reference ensures that variations in the excitation current do not
affect the measurement system since the input voltage from the
RTD and reference voltage across R

REF

vary ratiometrically with

the excitation current. Resistor R

REF

must, however, have a low

temperature coefficient to avoid errors in the reference voltage
overtemperature. R

REF

must also be large enough to generate at

least a 1 V voltage reference.

The preceding example shows just a single differential ADC
connection using a single reference input pair. The ADuC845/
ADuC847/ADuC848 have the capability of connecting to five
differential inputs directly or ten single-ended inputs (LFCSP
package only) as well as having a second reference input. This
arrangement means that different sensors with different
reference ranges can be connected to the part with the need for
external multiplexing circuitry. This arrangement is shown in
Figure 70. The bridge sensor shown can be a load cell or a
pressure sensor. The RTD is shown using a reference voltage
derived from the R

REF

resistor via the REFIN± inputs, and the

bridge sensor is shown using a divided down AV

reference via

the REFIN2± inputs.

ADuC845/ADuC847/ADuC848

Rev. A | Page 94 of 108

QuickStart DEVELOPMENT SYSTEM

The QuickStart Development System is an entry-level, low cost
development tool suite supporting the ADuC8xx MicroConverter
product family. The system consists of the following PC-based
(Windows® compatible) hardware and software development
tools:

Hardware:

Evaluation board and serial port
programming cable.

Software:

Serial download software.

Miscellaneous:

CD-ROM documentation and prototype
evaluation board.

A brief description of some of the software tools and
components in the QuickStart system follows.

Download--In-Circuit Serial Downloader

The serial downloader is a Windows application that allows the
user to serially download an assembled program (Intel® hexa-
decimal format file) to the on-chip program flash memory via
the serial COM port on a standard PC. Application Note uC004
details this serial download protocol and is available from

www.analog.com/microconverter

ASPIRE--IDE

The ASPIRE® integrated development environment is a
Windows application that allows the user to compile, edit, and
debug code in the same environment. The ASPIRE software
allows users to debug code execution on silicon using the
MicroConverter UART serial port. The debugger provides
access to all on-chip peripherals during a typical debug session
as well as single-step, animate (automatic single stepping), and
break-point code execution control.

Note that the ASPIRE IDE is also included as part of the
QuickStart-PLUS system. As part of the QuickStart-PLUS
system the ASPIRE IDE also supports mixed level and C source
debugging. This is not available in the QuickStart system where
the program is limited to assembly only.

QuickStart-PLUS DEVELOPMENT SYSTEM

The QuickStart-PLUS development system offers users
enhanced nonintrusive debug and emulation tools. The system
consists of the following PC-based (Windows compatible)
hardware and software development tools:

Hardware: Prototype

Board,

Accutron

NonIntrusive

Single-Pin Emulator.

Software:

ASPIRE Integrated Development
Environment. Features full C and Assembly
emulation using the Accutron single-pin
emulator.

Miscellaneous: CD-ROM

documentation.

ADuC845/ADuC847/ADuC848

Rev. A | Page 95 of 108

TIMING SPECIFICATIONS

AC inputs during testing are driven at DV

0.5 V for Logic 1 and 0.45 V for Logic 0. Timing measurements are made at V

min for

Logic 1 and V

max for Logic 0 as shown in Figure 71.

For timing purposes, a port pin is no longer floating when a 100 mV change from load voltage occurs. A port pin begins to float when a
100 mV change from the loaded V

level occurs as shown in Figure 71.

LOAD

for all outputs = 80 pF, unless otherwise noted.

= 2.7 V to 3.6 V or 4.75 V to 5.25 V, DV

= 2.7 V to 3.6 V or 4.75 V to 5.25 V; all specifications T

MIN

to T

MAX

, unless otherwise noted.

Table 64. CLOCK INPUT (External Clock Driven XTAL1) Parameter

32.768 kHz External Crystal

Min

Typ

Max

Unit

XTAL1

Period

30.52

µs

CKL

XTAL1

Width

Low

6.26

µs

CKH

XTAL1

Width

High

6.26

µs

CKR

XTAL1

Rise

Time

CKF

XTAL1

Fall

Time

1/t

CORE

Core Clock Frequency

0.098

1.57

12.58

MHz

CORE

Core Clock Period

0.636

µs

CYC

Machine

Cycle

Time

10.2

0.636

0.08

µs

ADuC845/ADuC847/ADuC848 internal PLL locks onto a multiple (512 times) of the 32.768 kHz external crystal frequency to provide a stable 12.58 MHz internal clock

for the system. The core can operate at this frequency or at a binary submultiple called Core_Clk, selected via the PLLCON SFR.

This number is measured at the default Core_Clk operating frequency of 1.57 MHz.

ADuC845/ADuC847/ADuC848 machine cycle time is nominally defined as 1/Core_Clk.

 0.5V

0.45V

0.2DV

+ 0.9V

TEST POINTS

0.2DV

 0.1V

LOAD

 0.1V

LOAD

+ 0.1V

TIMING

REFERENCE

POINTS

LOAD

 0.1V

LOAD

 0.1V

04741-0-077

Figure 71. Timing Waveform Characteristics

ADuC845/ADuC847/ADuC848

Rev. A | Page 105 of 108

ORDERING GUIDE

Model

Temperature Range

Package Description

Package Option

ADuC845BS62-5

-40°C to +125°C

52-Lead Plastic Quad Flatpack, 62-kbyte, 5 V

S-52

ADuC845BS62-3

-40°C to +125°C

52-Lead Plastic Quad Flatpack, 62-kbyte, 3 V

S-52

ADuC845BS8-5

-40°C to +125°C

52-Lead Plastic Quad Flatpack, 8-kbyte, 5 V

S-52

ADuC845BS8-3

-40°C to +125°C

52-Lead Plastic Quad Flatpack, 8-kbyte, 3 V

S-52

ADuC845BCP62-5

-40°C to +85°C

56-Lead Chip Scale Package, 62-kbyte, 5 V

CP-56

ADuC845BCP62-3

-40°C to +85°C

56-Lead Chip Scale Package, 62-kbyte, 3 V

CP-56

ADuC845BCP8-5

-40°C to +85°C

56-Lead Chip Scale Package, 8-kbyte, 5 V

CP-56

ADuC845BCP8-3

-40°C to +85°C

56-Lead Chip Scale Package, 8-kbyte, 3 V

CP-56

ADuC847BS62-5

-40°C to +125°C

52-Lead Plastic Quad Flatpack, 62-kbyte, 5 V

S-52

ADuC847BS62-3

-40°C to +125°C

52-Lead Plastic Quad Flatpack, 62-kbyte, 3 V

S-52

ADuC847BS32-5

-40°C to +125°C

52-Lead Plastic Quad Flatpack, 32-kbyte, 5 V

S-52

ADuC847BS32-3

-40°C to +125°C

52-Lead Plastic Quad Flatpack, 32-kbyte, 3 V

S-52

ADuC847BS8-5

-40°C to +125°C

52-Lead Plastic Quad Flatpack, 8-kbyte, 5 V

S-52

ADuC847BS8-3

-40°C to +125°C

52-Lead Plastic Quad Flatpack, 8-kbyte, 3 V

S-52

ADuC847BCP62-5

-40°C to +85°C

56-Lead Chip Scale Package, 62-kbyte, 5 V

CP-56

ADuC847BCP62-3

-40°C to +85°C

56-Lead Chip Scale Package, 62-kbyte, 3 V

CP-56

ADuC847BCP8-5

-40°C to +85°C

56-Lead Chip Scale Package, 8-kbyte, 5 V

CP-56

ADuC847BCP8-3

-40°C to +85°C

56-Lead Chip Scale Package, 8-kbyte, 3 V

CP-56

ADuC848BS62-5

-40°C to +125°C

52-Lead Plastic Quad Flatpack, 62-kbyte, 5 V

S-52

ADuC848BS62-3

-40°C to +125°C

52-Lead Plastic Quad Flatpack, 62-kbyte, 3 V

S-52

ADuC848BS32-5

-40°C to +125°C

52-Lead Plastic Quad Flatpack, 32-kbyte, 5 V

S-52

ADuC848BS32-3

-40°C to +125°C

52-Lead Plastic Quad Flatpack, 32-kbyte, 3 V

S-52

ADuC848BS8-5

-40°C to +125°C

52-Lead Plastic Quad Flatpack, 8-kbyte, 5 V

S-52

ADuC848BS8-3

-40°C to +125°C

52-Lead Plastic Quad Flatpack, 8-kbyte, 3 V

S-52

ADuC848BCP62-5

-40°C to +85°C

56-Lead Chip Scale Package, 62-kbyte, 5 V

CP-56

ADuC848BCP62-3

-40°C to +85°C

56-Lead Chip Scale Package, 62-kbyte, 3 V

CP-56

ADuC848BCP8-5

-40°C to +85°C

56-Lead Chip Scale Package, 8-kbyte, 5 V

CP-56

ADuC848BCP8-3

-40°C to +85°C

56-Lead Chip Scale Package, 8-kbyte, 3 V

CP-56

EVAL-ADuC845QS

QuickStart Development System

EVAL-ADuC845QSP

QuickStart-PLUS Development System

EVAL-ADuC847QS

QuickStart Development System

EVAL-ADuC847QSP

QuickStart-PLUS Development System

The -3 and -5 in the Model column indicate the DV

operating voltage.

The QuickStart Plus system can only be ordered directly from Accutron. It can be purchased from the website www.accutron.com.

РР»РµРєС‚СЂРѕРЅРЅС‹Р№ РєРѕРјРїРѕРЅРµРЅС‚: ADuC847

Document Outline

Р­Р»РµРєС‚СЂРѕРЅРЅС‹Р№ РєРѕРјРїРѕРЅРµРЅС‚: ADuC847

Document Outline

РР»РµРєС‚СЂРѕРЅРЅС‹Р№ РєРѕРјРїРѕРЅРµРЅС‚: ADuC847