Parallel-Port 16-Bit

SoundPort

Stereo Codec

AD1845

FEATURES
Single-Chip Integrated

Digital Audio Stereo Codec

Microsoft

and Windows

Sound System Compatible

MPC Level-2+ Compliant Mixing
16 mA Bus Drive Capability
Supports Two DMA Channels for Full Duplex Operation
On-Chip Capture and Playback FIFOs
Advanced Power-Down Modes
Programmable Gain and Attenuation
Sample Rates from 4.0 kHz to 50 kHz Derived from a

Single Clock or Crystal Input

68-Lead PLCC, 100-Lead TQFP Packages
Operation from +5 V Supplies
Byte-Wide Parallel Interface to ISA and EISA Buses
Pin Compatible with AD1848, AD1846, CS4248, CS4231

REV. C

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
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.

PRODUCT OVERVIEW

The Parallel Port AD1845 SoundPort

Stereo Codec integrates

key audio data conversion and control functions into a single
integrated circuit. The AD1845 provides a complete, single chip
computer audio solution for business audio and multimedia
applications. The codec includes stereo audio converters, com-

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A
Tel: 781/329-4700

World Wide Web Site: http://www.analog.com

Fax: 781/326-8703

© Analog Devices, Inc., 1997

(Continued on Page 9)

SoundPort is a registered trademark of Analog Devices, Inc.
Microsoft and Windows are registered trademarks of Microsoft Corporation.

plete on-chip filtering, MPC Level-2 compliant analog mixing,
programmable gain, attenuation and mute, a variable sample
frequency generator, FIFOs, and supports advanced power-
down modes. It provides a direct, byte-wide interface to both
ISA ("AT") and EISA computer buses for simplified implemen-
tation on a computer motherboard or add-in card.

The AD1845 SoundPort Stereo Codec supports a DMA re-
quest/grant architecture for transferring data with the host com-
puter bus. One or two DMA channels can be supported.
Programmed I/O (PIO) mode is also supported for control
register accesses and for applications lacking DMA control.
Two input control lines support mixed direct and indirect ad-
dressing of thirty-seven internal control registers over this asyn-
chronous interface. The AD1845 includes dual DMA count
registers for full duplex operation enabling the AD1845 to cap-
ture data on one DMA channel and play back data on a separate
channel. The FIFOs on the AD1845 reduce the risk of losing
data when making DMA transfers over the ISA/EISA bus. The
FIFOs buffer data transfers and allow for relaxed timing in
acknowledging requests for capture and playback data.

FUNCTIONAL BLOCK DIAGRAM

GAM = GAIN
ATTENTUATE
MUTE

DIGITAL MIX
ATTENUATE

VARIABLE SAMPLE

FREQUENCY GENERATOR

MUTE

M_IN

L_AUX2

R_AUX2

L_MIC

R_MIC

ANALOG SUPPLY

0 dB/
20 dB

GAM

A/D

CONVERTER

GAIN

CONTROL

REGISTERS

HOST DMA
INTERRUPT

REFERENCE

L_OUT

M_OUT

R_OUT

L_LINE

R_LINE

L_AUX1

R_AUX1

AD1845

DIGITAL SUPPLY

CLOCK SOURCE

POWER DOWN

RESET

DIGITAL

ANALOG

BUS DRIVER
CONTROL

GAIN

EXTERNAL
CONTROL

REF

REF_F

GAM

A/D

CONVERTER

ATTENUATE

MUTE

D/A

CONVERTER

ATTENUATE

MUTE

D/A

CONVERTER

-LAW

A-LAW

LINEAR

FIFO

-LAW

A-LAW

LINEAR

PLAYBACK ACK

CAPTURE ACK

PLAYBACK REQ

CAPTURE REQ

ADR1:0

DATA7:0

FIFO

P
A
R
A
L
L
E
L

O
R

U
X

AD1845SPECIFICATIONS

STANDARD TEST CONDITIONS UNLESS OTHERWISE NOTED

Temperature

Digital Supply (V

)

5.0

Analog Supply (V

)

5.0

Word Rate (F

)

kHz

Input Signal

1008

Analog Output Passband

20 Hz to 20 kHz

ADC FFT Size

2048

DAC FFT Size

8192

ANALOG INPUT

Min

Typ

Max

Units

Input Voltage (RMS Values Assume Sine Wave Input)

Line

V rms

2.55

2.83

3.35

V p-p

MIC with +20 dB Gain (MGE = 1)

0.1

V rms

0.255

0.283

0.335

V p-p

MIC with 0 dB Gain (MGE = 0)

V rms

2.55

2.83

3.35

V p-p

Input Impedance*

Input Capacitance

PROGRAMMABLE GAIN AMPLIFIERADC

Min

Typ

Max

Units

Step Size (All Steps Tested)

(0 dB to 22.5 dB)

0.7

1.5

1.9

PGA Gain Range Span

21.5

22.5

23.5

AUXILIARY LINE, MONO, AND MICROPHONE INPUT ANALOG GAIN/AMPLIFIERS/ATTENUATORS

Min

Typ

Max

Units

Step Size : AUX1, AUX2, LINE, MIC (All Steps Tested)

(+12 dB to 30 dB)

1.25

1.5

1.75

(31.5 dB to 34.5 dB)

1.5

2.0

Step Size: M_IN (All Steps Tested)

(0 dB to 39 dB)

2.5

3.0

3.6

(42 dB to 45 dB)

2.2

3.0

3.85

Input Gain/Attenuation Range: AUX1, AUX2, LINE, MIC

45.0

46.5

49.0

Input Gain/Attenuation Range: M_IN

DIGITAL DECIMATION AND INTERPOLATION FILTERS*

Min

Max

Units

Passband

0.4

Passband Ripple

0.1

Transition Band

0.4

0.6

Stopband

0.6

Stopband Rejection

Group Delay

15/F

Group Delay Variation Over Passband

0.0

*Guaranteed, not tested.

DAC Test Conditions

Calibrated
0 dB Relative to Full Scale
16-Bit Linear Mode
10 k

Output Load

Mute Off, OL = 0

ADC Test Conditions

Calibrated
0 dB Gain
1.0 dB Relative to Full Scale
Line Input
16-Bit Linear Mode

REV. C

ANALOG-TO-DIGITAL CONVERTERS

Min

Typ

Max

Units

Resolution

Bits

Dynamic Range (60 dB Input, THD+N Referenced to Full Scale, A-Weighted)

THD+N (Referenced to Full Scale)

0.025

Signal-to-Intermodulation Distortion

ADC Crosstalk*

Line Inputs (Input L, Ground R, Read R; Input R, Ground L, Read L)

Line to MIC (Input LINE, Ground and Select MIC, Read ADC)

Line to AUX1

Line to AUX2

Gain Error (Full-Scale Span Relative to Nominal Input Voltage)

18.5

+10

Interchannel Gain Mismatch (Difference of Gain Errors)

0.9

ADC Offset Error

DIGITAL-TO-ANALOG CONVERTERS

Min

Typ

Max

Units

Resolution

Bits

Dynamic Range (60 dB Input, THD+N Referenced to Full Scale, A-Weighted)

THD+N (Referenced to Full Scale)

0.032

Signal-to-Intermodulation Distortion

Gain Error (Full-Scale Span Relative to Nominal Output Voltage)

14.5

+10

Interchannel Gain Mismatch (Difference of Gain Errors)

0.6

DAC Crosstalk* (Input L, Zero R, Measure R_OUT; Input R, Zero L, Measure L_OUT)

Total Out-of-Band Energy (Measured from 0.6

to 100 kHz)*

Audible Out-of-Band Energy (Measured from 0.6

to 20 kHz)*

DAC ATTENUATOR

Min

Typ

Max

Units

Step Size (0 dB to 22.5 dB)

1.3

1.5

1.7

Step Size (22.5 dB to 94.5 dB)*

1.0

1.5

2.0

Output Attenuation Range Span*

93.5

94.5

95.5

ANALOG OUTPUT

Min

Typ

Max

Units

Full-Scale Output Voltage

OL = 0

1.7

2.0

2.2

V p-p

OL = 1

2.4

2.83

3.11

V p-p

Output Impedance*

600

External Load Impedance

Output Capacitance*

External Load Capacitance

100

REF

2.05

2.25

2.60

REF

Current Drive

100

REF

Output Impedance

Mute Attenuation of 0 dB Fundamental* (L_OUT, R_OUT, M_OUT)

Mute Click (Muted Output Minus Unmuted Midscale DAC Output)*

*Guaranteed, not tested.

AD1845

REV. C

POWER SUPPLY

Min

Typ

Max

Units

Power Supply RangeDigital and Analog

4.75

5.25

Power Supply Current

130

Analog Supply Current

Digital Supply Current

Power Dissipation

(Current

Nominal Supplies)

650

Power-Down Supply Current

Reset Supply Current

Total Power-Down Supply Current

Standby Supply Current

Mixer Power-Down Supply Current

Mixer Only Supply Current

ADC Power-Down Supply Current

DAC Power-Down Supply Current

Power Supply Rejection (100 mV p-p Signal @ 1 kHz)*

(At Both Analog and Digital Supply Pins, both ADCs and DACs)

CLOCK SPECIFICATIONS*

Min

Max

Units

Input Clock Frequency

MHz

Recommended Clock Duty Cycle

Power Up Initialization Time

512

*Guaranteed, not tested.
Specifications subject to change without notice.

AD1845

REV. C

ORDERING GUIDE

Temperature

Package

Model

Range

Description

Option

AD1845JP

C to +70

68-Lead PLCC

P-68A

AD1845JP-REEL

C to +70

68-Lead PLCC

P-68A

AD1845JST

C to +70

100-Lead TQFP

ST-100

NOTES

P = Plastic Leaded Chip Carrier; ST = Thin Quad Flatpack.

13" Reel, multiples of 250 pcs.

ENVIRONMENTAL CONDITIONS

Ambient Temperature Rating:

AMB

= T

CASE

(PD

)

CASE

= Case Temperature in

PD = Power Dissipation in W

= Thermal Resistance (Case-to-Ambient)

= Thermal Resistance (Junction-to-Ambient)

= Thermal Resistance (Junction-to-Case)

Package

PLCC

C/W

TQFP

C/W

ABSOLUTE MAXIMUM RATINGS*

Min

Max

Units

Power Supplies

Digital (V

)

0.3

6.0

Analog (V

)

0.3

6.0

Input Current

(Except Supply Pins)

10.0

Analog Input Voltage (Signal Pins)

0.3

+0.3

Digital Input Voltage (Signal Pins)

0.3

+0.3

Ambient Temperature (Operating)

+70

Storage Temperature

+150

*Stresses greater than 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 indicated in the
operational section of this specification is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect device reliability.

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 the AD1845 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.

WARNING!

ESD SENSITIVE DEVICE

AD1845

REV. C

PIN DESIGNATIONS

100

XCTL1

INT

XCTL0

GNDD

M_OUT

M_IN

GNDD

AD1845

TOP VIEW

(Not to Scale)

NC = NO CONNECT

ADR0

CDAK

CDRQ

PDAK

PDRQ

GNDD

XTAL1I

XTAL1O

GNDD

XTAL2I

XTAL2O

PWRDWN

RESET

GNDD

R_FILT

ADR1

GNDD

DATA0

DATA1

DATA2

DATA3

GNDD

DATA4

DATA5

DATA6

DATA7

GNDD

DBEN

DBDIR

R_LINE

R_MIC

L_MIC

L_LINE

L_FILT

REF

REF_F

GNDA

L_AUX2

L_AUX1

L_OUT

R_OUT

R_AUX1

R_AUX2

XCTL1

INT

XCTL0

GNDD

M_OUT

M_IN

GNDD

AD1845

TOP VIEW

(Not to Scale)

NC = NO CONNECT

ADR0

CDAK

CDRQ

PDAK

PDRQ

GNDD

XTAL1I

XTAL1O

GNDD

XTAL2I

XTAL2O

PWRDWN

RESET

GNDD

R_FILT

ADR1

GNDD

DATA0

DATA1

DATA2

DATA3

GNDD

DATA4

DATA5

DATA6

DATA7

GNDD

DBEN

DBDIR

R_LINE

R_MIC

L_MIC

L_LINE

L_FILT

REF

REF_F

GNDA

L_AUX2

L_AUX1

L_OUT

R_OUT

R_AUX1

R_AUX2

100-Lead TQFP

68-Lead PLCC

AD1845

REV. C

PIN FUNCTION DESCRIPTIONS

Parallel Interface

Pin Name

PLCC

TQFP

I/O

Description

CDRQ

Capture Data Request. The assertion of this signal HI indicates that the codec has a cap-
tured audio sample from the ADC ready for transfer. This signal will remain asserted
until the internal capture FIFO is empty.

CDAK

Capture Data Acknowledge. The assertion of this active LO signal indicates that the

cycle occurring is a DMA read from the capture buffer.

PDRQ

Playback Data Request. The assertion of this signal HI indicates that the codec is ready
for more DAC playback data. The signal will remain asserted until the internal playback
FIFO is full.

PDAK

Playback Data Acknowledge. The assertion of this active LO signal indicates that the

cycle occurring is a DMA write to the playback buffer.

ADR1:0

9 & 10

100 & 1

Codec Addresses. These address pins are asserted by the codec interface logic during a
control register/PIO access. The state of these address lines determine which direct
register is accessed.

Read Command Strobe. This active LO signal defines a read cycle from the codec. The
cycle may be a read from the control/PIO registers, or the cycles could be a read from
the codec's DMA sample registers.

Write Command Strobe. This active LO signal indicates a write cycle to the codec. The
cycle may be a write to the control/PIO registers, or the cycle could be a write to the
codec's DMA sample registers.

AD1845 Chip Select. The codec will not respond to any control/PIO cycle accesses
unless this active LO signal is LO. This signal is ignored during DMA transfers.

DATA7:0

36 &

8487 &

I/O

Data Bus. These pins transfer data and control information between the codec and

6568

9093

the host.

DBEN

Data Bus Enable. This pin enables the external bus drivers. This signal is normally HI.

For control register/PIO cycles,

DBEN = (WR or RD) and CS

For DMA cycles,

DBEN = (WR or RD) and (PDAK or CDAK).

DBDIR

Data Bus Direction. This pin controls the direction of the data bus transceiver. HI
enables writes from the host bus to the AD1845; LO enables reads from the AD1845 to
the host bus. This signal is normally HI.

For control register/PIO cycles,

DBDIR =

RD and CS

For DMA cycles,

DBDIR =

RD and (PDAK or CDAK).

AD1845

REV. C

Analog Signals

Pin Name

PLCC

TQFP

I/O

Description

L_LINE

Left Line Input.

R_LINE

Right Line Input.

L_MIC

Left Microphone Input. This signal can be either line level or 20 dB from line level
(using the on-chip 20 dB gain block).

R_MIC

Right Microphone Input. This signal can be either line level or 20 dB from line level
(using the on-chip 20 dB gain block).

L_AUX1

Left Auxiliary #1 Line Input.

R_AUX1

Right Auxiliary #1 Line Input.

L_AUX2

Left Auxiliary #2 Line Input.

R_AUX2

Right Auxiliary #2 Line Input.

L_OUT

Left Line Output.

R_OUT

Right Line Output.

M_IN

Mono Input.

M_OUT

Mono Output.

Miscellaneous

Pin Name

PLCC

TQFP

I/O

Description

XTAL1I

24.576 MHz Crystal #1 Input.

XTAL1O

24.576 MHz Crystal #1 Output.

XTAL2I

Not used on the AD1845.

XTAL2O

Not used on the AD1845.

PWRDWN

Power Down Signal. Active LO places the AD1845 in its lowest power consumption
mode. All sections of the AD1845, including the digital interface, are shut down and
consume minimal power.

INT

Host Interrupt Pin. A host interrupt is generated to notify the host that a specified
event has occurred.

XCTL1:0

58 & 56 73 & 71

External Control. These signals reflect the current status of register bits inside the
AD1845. They can be used for signaling or to control external logic.

RESET

Reset. Active LO resets all digital registers and filters, and resets all analog filters. Active
LO places the AD1845 in the lowest power consumption mode. XTAL1 is required to be
running during the minimum low pulsewidth of the reset signal.

REF

Voltage Reference. Nominal 2.25 volt reference available for dc-coupling and level-
shifting. V

REF

should not be used to sink or source current.

REF_F

Voltage Reference Filter. Voltage reference filter point for external bypassing only.

L_FILT

Left Channel Filter. This pin requires a 1.0

F capacitor to analog ground for proper

operation.

R_FILT

Right Channel Filter. This pin requires a 1.0

F capacitor to analog ground for proper

operation.

4852,

25, 2124

No Connect.

26, 27, 32, 34,
36, 37, 39,
5053, 5866,
69, 70, 8083,
9497

AD1845

REV. C

Power Supplies

Pin Name

PLCC

TQFP

I/O

Description

35 & 36

41 & 42

Analog Supply Voltage (+5 V).

GNDA

34 & 37

40 & 43

Analog Ground.

1, 7, 15,

10, 14,

Digital Supply Voltage (+5 V).

19, 45,

55, 68,

88, 98

GNDD

2, 8, 16,

11, 15, 20,

Digital Ground.

20, 25,

54, 67,

44, 53,

79, 89,

(Continued from page 1)

unsigned magnitude PCM linear data, and 8-bit

-law or A-law

companded digital data.

The

DACs are preceded by a digital interpolation filter. An

attenuator provides independent user volume control over each
DAC channel. Nyquist images and shaped quantized noise are
removed from the DACs' analog stereo output by on-chip
switched-capacitor and continuous-time filters.

The AD1845 supports multiple low power and power-down
modes to support notebook and portable computing multimedia
applications. The ADC, DAC, and mixer paths can be sus-
pended independently allowing the AD1845 to be used for
capture-only or playback-only, lessening power consumption
and extending battery life.

The AD1845 includes a variable sample frequency generator,
that allows the codec to instantaneously change sample rates
with a resolution of 1 Hz without "clicks" and "pops." Addi-
tionally,

quantization noise is kept out of the 20 kHz audio

band regardless of the chosen sample rate. The codec uses the
variable sample frequency generator to derive all internal clocks
from a single external crystal or clock source.

Expanded Mode (MODE2)

MODE1 is the initial state of the AD1845. In this state the
AD1845 appears as an AD1848 compatible device. To access
the expanded modes of operation on the AD1845, the MODE2
bit should be set in the Miscellaneous Information Control
Register. When this bit is set to one, 16 additional indirect
registers can be addressed allowing the user to access the
AD1845's expanded features. The AD1845 can return to
MODE1 operation by clearing the MODE2 bit. In both
MODE1 and MODE2, the capture and playback FIFOs are
active to prevent data loss.

The additional MODE2 functions are:

1. Full-Duplex DMA support.

2. MIC input mixer, mute and volume control.

3. Mono output with mute control.

4. Mono input with mixer volume control.

5. Software controlled advanced power-down modes.

6. Programmable sample rates from 4 kHz to 50 kHz in 1 Hz
increments.

ADDRESS

DECODE

DATA7:0

DBDIR

DBEN

PDRQ

CDRQ

PDAK

CDAK

INT

AD1845

AEN

SA19:2

SA1

SA0

IOWC

IORC

DATA7:0

DRQ <X>

DRQ <Y>

DAK <X>

DAK <Y>

IRQ <Z>

74_245

DIR

S
A

B
U
S

Figure 1. Interface to ISA Bus

External circuit requirements are limited to a minimal number
of low cost support components. Anti-imaging DAC output
filters are incorporated on-chip. Dynamic range exceeds 80 dB
over the 20 kHz audio band. Sample rates from 4 kHz to 50 kHz
are supported from a single external crystal or clock source.

The AD1845 has built-in 8/16 mA (user selectable) bus drivers.
If 24 mA drive capability is required, the AD1845 generates
enable and direction controls for IC bus buffers such as the
74 245.

The codec includes a stereo pair of

analog-to-digital con-

verters and a stereo pair of

digital-to-analog converters. The

AD1845 mixer surpasses MPC Level-2 recommendations.
Inputs to the ADC can be selected from four stereo pairs of
analog signals: line (LINE), microphone (MIC), auxiliary line
#1 (AUX1), and post-mixed DAC output. A software-con-
trolled programmable gain stage allows independent gain for
each channel going into the ADC. In addition, the analog mixer
allows the mono input (M_IN), MIC, AUX1, LINE and auxil-
iary line #2 (AUX2) signals to be mixed with the DACs' output.
The ADCs' output can be digitally mixed with the DACs' input.

The pair of 16-bit outputs from the ADCs is available over a
byte-wide bidirectional interface that also supports 16-bit digital
input to the DACs and control information. The AD1845 can
accept and generate 16-bit twos complement PCM linear digital
data in both little endian or big endian byte ordering, 8-bit

AD1845

REV. C

Digital Mixing

Stereo digital output from the ADCs can be digitally mixed with
the input to the DACs. Digital output from the ADCs going out
of the data port is unaffected by the digital mix. Along the
digital mix datapath, the 16-bit linear output from the ADCs
is attenuated by an amount specified with control bits. Both
channels of the digital mix datapath are attenuated by the same
amount. (Note that internally the AD1845 always works with
16-bit PCM linear data, digital mixing included; format conver-
sions take place at the input and output.)

Sixty-four steps of 1.5 dB attenuation are supported to 94.5 dB.
The digital mix datapath can also be completely muted. Note
that the level of the mixed signal is also a function of the input
PGA settings, since they affect the ADCs' output.

The attenuated digital mix data is digitally summed with the
DAC input data prior to the DACs' datapath attenuators. The
digital sum of digital mix data and DAC input data is clipped at
plus or minus full scale and does not wrap around. Because both
stereo signals are mixed before the output attenuators, mix data is
attenuated a second time by the DACs' datapath attenuators.

In case the AD1845 is capturing data, but ADC output data is
not removed in time ("ADC overrun"), the last sample captured
before overrun will be used for the digital mix. In case the
AD1845 is playing back data, but input digital DAC data fails
to arrive in time ("DAC underrun"), a midscale zero will be
added to the digital mix data when the DACZ control bit is set
to 0; otherwise, the DAC will output the previous valid sample
in an underrun condition.

Analog Outputs

Stereo and mono line-level outputs are available at external
pins. Each channel of this output can be independently muted.
When muted, the outputs will settle to a dc value near V

REF

, the

midscale reference voltage. The output is selectable for 2.0 V
peak-to-peak or 2.8 V peak-to-peak. When selecting the LINE
output as an input to the ADC, the ADC automatically com-
pensates for the output level selection.

Digital Data Types

The AD1845 supports five global data types: 16-bit twos comple-
ment linear PCM (little endian and big endian byte ordering),
8-bit unsigned linear PCM, companded

-law, and 8-bit com-

panded A-law, as specified by control register bits. Data in all
formats is always transferred MSB first. All data formats that are
less than 16 bits are MSB-aligned to ensure the use of full
system resolution.

The 16-bit PCM data format is capable of representing 96 dB
of dynamic range. Eight-bit PCM can represent 48 dB of dy-
namic range. Companded

-law and A-law data formats use

nonlinear coding with less precision for large amplitude signals.
The loss of precision is compensated for by an increase in dy-
namic range to 64 dB and 72 dB, respectively.

On input, 8-bit companded data is expanded to an internal
linear representation, according to whether

-law or A-law was

specified in the codec's internal registers. Note that when

-law

compressed data is expanded to a linear format, it requires
14 bits. A-law data expanded requires 13 bits.

FUNCTIONAL DESCRIPTION

This section overviews the functionality of the AD1845 and is
intended as a general introduction to the capabilities of the
device. As much as possible, detailed reference information has
been placed in "Control Registers" and other sections. The
user is not expected to refer repeatedly to this section.

Analog Inputs

The AD1845 SoundPort Stereo Codec accepts stereo line-level
and microphone-level inputs. The LINE, MIC, AUX1, and
post-mixed DAC output are available to the ADC multiplexer.
The DAC output can be mixed with LINE, MIC, AUX1,
AUX2 and M_IN. Each channel of the MIC inputs can be
amplified by +20 dB to compensate for the difference between
line levels and typical condenser microphone levels.

Analog Mixing

The M_IN mono input signal, MIC, LINE, AUX1 and AUX2
analog stereo signals can be mixed in the analog domain with
the DAC output. Each channel of each AUX, LINE and MIC
analog input can be independently gained/attenuated from
+12 dB to 34.5 dB in 1.5 dB steps or completely muted.
M_IN can be attenuated from 0 dB to 45 dB in 3 dB steps or
muted. The post-mixed DAC outputs are available on L_OUT
and R_OUT and also to the ADC input multiplexer.

Even if the AD1845 is not playing back data from its DACs, the
analog mix function can still be active.

Analog-to-Digital Datapath

The PGA following the input multiplexer allows independent
selectable gains for each channel from 0 dB to 22.5 dB in
+1.5 dB steps. The codec can operate either in a global stereo
mode or in a global mono mode with left-channel inputs
appearing at both channel outputs.

The AD1845

ADCs incorporate a fourth-order modulator.

A single pole of passive filtering is all that is required for anti-
aliasing the analog input because of the ADC's high over sam-
pling ratio. The ADCs include linear-phase digital decimation
filters that low-pass filter the input to 0.4

. ("F

" is the

word rate or "sampling frequency.") ADC input over range
conditions are reported on status bits in the Test and Initializa-
tion Register.

Digital-to-Analog Datapath

The

DACs are preceded by a programmable attenuator and

a low-pass digital interpolation filter. The anti-imaging interpo-
lation filter over samples and digitally filters the higher fre-
quency images. The attenuator allows independent control of
each DAC channel from 0 dB to 94.5 dB in 1.5 dB steps plus
full mute. The DACs'

noise shapers also over sample and

convert the signal to a single-bit stream. The DAC outputs are
then filtered in the analog domain by a combination of switched-
capacitor and continuous-time filters. They remove the very
high frequency components of the DAC bit stream output. No
external components are required.

Changes in DAC output attenuation take effect only on zero
crossings, eliminating "zipper" noise on playback. Each chan-
nel has its own independent zero-crossing detector and attenua-
tor change control circuitry. A timer guarantees that requested
volume changes will occur even in the absence of a zero cross-
ing. The time-out period is 8 milliseconds at a 48 kHz sampling
rate and 48 milliseconds at an 8 kHz sampling rate. (Timeout
[ms]

384

[kHz].)

AD1845

REV. C

MSB

LSB

COMPRESSED

INPUT DATA

8 7

MSB

LSB

3/2 2/1

EXPANSION

MSB

LSB

3/2 2/1

DAC INPUT

0 0 0 / 0 0

Figure 2.

-Law or A-Law Expansion

When 8-bit companding is specified, the ADCs' linear output is
compressed to the format specified.

MSB

LSB

MSB

LSB

3/2 2/1

MSB

LSB

8 7

0 0 0 0 0 0 0 0

ADC OUTPUT

TRUNCATION

COMPRESSION

Figure 3.

-Law or A-Law Compression

Note that all format conversions take place at input or output.
Internally, the AD1845 always uses 16-bit linear PCM represen-
tations to maintain maximum precision.

Timer Registers

The timer registers are provided for system level synchroniza-
tion, and for periodic interrupt generation. The 16-bit timer
time base is determined by the frequency of the connected input
clock source.

The timer is enabled by setting the Timer Enable bit, TE, in the
Alternate Feature Enable register. To set the timer, load the
Upper and Lower Timer Bits Registers. The timer value will
then be loaded into an internal count register with a value of
approximately 10

s (the exact timer value is listed in the regis-

ter descriptions). The internal count register will decrement
until it reaches zero, then the Timer Interrupt bit, TI, is set and
an interrupt will be sent to the host. The next timer clock will
load the internal count register with the value of the Timer
Register, and the timer will be reinitialized. To clear the inter-
rupt, write to the Status Register or write a "0" to TI.

Interrupts

The AD1845 supports interrupt conditions generated by DMA
playback count expiration, DMA capture count expiration, or
timer expiration. The INT bit will remain set, HI, until a write
has been completed to the Status Register or by clearing the TI,
CI, or PI bit (depending on the existing condition) in the Cap-
ture Playback Timer Register. The IEN bit of the Pin Control
Register determines whether the interrupt pin responds to an
interrupt condition and reflects the interrupt state on the
INT status bit.

Power Supplies and Voltage Reference

The AD1845 operates from a +5 V power supply. Independent
analog and digital supplies are recommended for optimal perfor-
mance though excellent results can be obtained in single-supply
systems. A voltage reference is included on the codec and its
2.25 V buffered output is available on an external pin (V

REF

The reference output can be used for biasing op amps used in
dc coupling. The internal reference is externally bypassed to
analog ground at the V

REF_F

pin.

Clocks and Sample Rates

The AD1845 operates from a single external crystal or clock
source. From a single input, a wide range of sample rates can be
generated. The AD1845 default frequency source is a
24.576 MHz input. The AD1845 can also be driven from a
14.31818 MHz (OSC), 24 MHz, 25 MHz or 33 MHz input
frequency source. In MODE1, the input drives the internal
variable sample frequency generator to derive the following
AD1848 compatible sample rates: 5.5125, 6.615, 8, 9.6,
11.025, 16, 18.9, 22.05, 27.42857, 32, 33.075, 37.8, 44.1,
48 kHz. In MODE2, the AD1845 can be programmed to gen-
erate any sample frequency between 4 kHz and 50 kHz with
1 Hz resolution. Note that it is no longer required to enter
Mode Change Enable (MCE) to change the sample rate. This
feature allows the user to change the AD1845's sample rate "on
the fly."

CONTROL REGISTERS
Control Register Architecture

The AD1845 SoundPort Stereo Codec accepts both data and
control information through its byte-wide parallel port. Indirect
addressing minimizes the number of external pins required to
access all 37 of its byte-wide internal registers. Only two exter-
nal address pins, ADR1:0, are required to accomplish all data
and control transfers. These pins select one of five direct regis-
ters. (ADR1:0 = 3 addresses two registers, depending on
whether the transfer is for a playback or capture.)

ADR1:0

Register Name

Index Address Register

Indexed Data Register

Status Register

PIO Data Register

Figure 4. Direct Register Map

AD1845

REV. C

A write to or a read from the Indexed Data Register will access the Indirect Register which is indexed by the value most recently
written to the Index Address Register. The Status Register and the PIO Data Register are always accessible directly, without
indexing. The 32 Indirect Register indexes are shown in Figure 5:

Index

Register Name

Reset/Default State

Left Input Control

000x

0000

Right Input Control

000x

0000

Left Aux #1 Input Control

1xx0

1000

Right Aux #1 Input Control

1xx0

1000

Left Aux #2 Input Control

1xx0

1000

Right Aux #2 Input Control

1xx0

1000

Left Output Control

1x00

0000

Right Output Control

1x00

0000

Clock and Data Format

0000

Interface Configuration

00xx

1000

Pin Control

00xx

xx00

Test and Initialization

0000

Miscellaneous Information

10x0

1010

Digital Mix/Attenuation

0000

00x0

Upper Base Count

0000

Lower Base Count

0000

Alternate Feature Enable/Left MIC Input Control

0001

MIC Mix Enable/Right MIC Input Control

0001

000x

Left Line Gain, Attenuate, Mute, Mix

1xx0

1000

Right Line Gain, Attenuate, Mute, Mix

1xx0

1000

Lower Timer

0000

Upper Timer

0000

Upper Frequency Select

0001

1111

Lower Frequency Select

0100

0000

Capture Playback Timer

x000

0000

Revision ID

100x

x000

Mono Control

00xx

0011

Power-Down Control

000x

0xxx

Capture Data Format Control

0000

xxxx

Crystal Clock Select/Total Power-Down

000x

xxx0

Capture Upper Base Count

0000

Capture Lower Base Count

0000

"x" indicates reserved bit, always write "0s" to these bits.

Figure 5. Indirect Register Map and Reset/Default States

A detailed map of all direct and indirect register contents is summarized for reference as follows:

AD1845

REV. C

Figure 6. Register Summary

Direct Registers

ADRl:0

Data 7

Data 6

Data 5

Data 4

Data 3

Data 2

Data 1

Data 0

INIT

MCE

TRD

IXA4

IXA3

IXA2

IXA1

IXA0

IXD7

IXD6

IXD5

IXD4

IXD3

IXD2

IXD1

IXD0

CU/L

CL/R

CRDY

SOUR

PU/L

PL/R

PRDY

INT

CD7

CD6

CD5

CD4

CD3

CD2

CD1

CD0

PD7

PD6

PD5

PD4

PD3

PD2

PD1

PD0

Indirect Registers

IXA3:0

Data 7

Data 6

Data 5

Data 4

Data 3

Data 2

Data 1

Data 0

LSS1

LSS0

LMGE

res

LIG3

LIG2

LIG1

LIG0

RSS1

RSS0

RMGE

res

RIG3

RIG2

RIG1

RIG0

LMX1

res

LX1A4

LX1A3

LX1A2

LX1A1

LX1A0

RMX1

res

RX1A4

RX1A3

RX1A2

RX1A1

RX1A0

LMX2

res

LX2A4

LX2A3

LX2A2

LX1A1

LX2A0

RMX2

res

RX2A4

RX2A3

RX2A2

RX2A1

RX2A0

LDM

res

LDA5

LDA4

LDA3

LDA2

LDA1

LDA0

RDM

res

RDA5

RDA4

RDA3

RDA2

RDA1

RDA0

FMT1

FMT0

C/L

S/M

CFS2

CFS1

CFS0

CSS

CPIO

PPIO

res

ACAL

SDC

CEN

PEN

XCTL1

XCTL0

res

IEN

INITD

COR

PUR

ACI

DRS

ORR1

ORR0

ORL1

ORL0

MID

MODE2

BUF8

res

ID3

ID2

ID1

ID0

DMA5

DMA4

DMA3

DMA2

DMA1

DMA0

res

DME

UB7

UB6

UB5

UB4

UB3

UB2

UB1

UB0

LB7

LB6

LB5

LB4

LB3

LB2

LB1

LB0

Expanded Mode (Requires MODE2=1)

LMG4

LMG3

LMG2

LMG1

LMG0

DACZ

LMME

RMME

RMG4

RMG3

RMG2

RMG1

RMG0

res

LLM

res

LLG4

LLG3

LLG2

LLG1

LLG0

RLM

res

RLG4

RLG3

RLG2

RLG1

RLG0

TL7

TL6

TL5

TL4

TL3

TL2

TL1

TL0

TU7

TU6

TU5

TU4

TU3

TU2

TU1

TU0

FU7

FU6

FU5

FU4

FU3

FU2

FU1

FU0

FL7

FL6

FL5

FL4

FL3

FL2

FL1

FL0

res

CID2

CID1

CID0

MIM

MOM

res

MIA3

MIA2

MIA1

MIA0

ADCPWD

DACPWD

MIXPWD

res

FREN

res

CFMT1

CFMT0

CC/L

CS/M

res

XFS2

XFS1

XFS0

res

TOTPWD

CUB7

CUB6

CUB5

CUB4

CUB3

CUB2

CUB1

CUB0

CLB7

CLB6

CLB5

CLB4

CLB3

CLB2

CLB1

CLB0

Note that the only sticky bit in any of the AD1845 control registers is the interrupt (INT) bit. All other bits can change with every
sample period.

AD1845

REV. C

DIRECT CONTROL REGISTER DEFINITIONS

Index Address Register (ADR1:0 = 0)

ADR1:0

Data 7

Data 6

Data 5

Data 4

Data 3

Data 2

Data 1

Data 0

INIT

MCE

TRD

IXA4

IXA3

IXA2

IXA1

IXA0

IXA4:0

Index Address. These bits define the address of the AD1845 register accessed by the Indexed Data Register.
These bits are read/write. IXA4 is not active in MODE1. Always write 0 to this bit when using the AD1845 in
MODE1.

TRD

Transfer Request Disable. This bit, when set, causes PIO and DMA transfers to cease when the Interrupt Status
(INT) bit of the Status Register is set.

Transfers Enabled During Interrupt. PDRQ and CDRQ pin outputs are generated uninhibited by interrupts.
DMA Current Counter Register decrements with every sample transferred when either PEN or CEN are enabled.

Transfers Disabled By Interrupt. PDRQ and CDRQ pin outputs are generated only if INT bit is 0 (when
either PEN or CEN, respectively are enabled). Any pending playback or capture requests are allowed to
complete at the time when INT is set. After pending requests complete, the data in the FIFO will be con-
sumed at the sample rate. Subsequently, the midscale inputs will be internally generated for the DACs if
the DACZ bit is set, otherwise, the previous valid sample will be repeated, and the ADC output buffer will
contain the last valid output. Clearing the sticky INT bit (or the TRD bit) will cause the resumption of
playback and/or capture requests (presuming PEN and/or CEN are enabled). The DMA Current Counter
Register will not decrement while both the TRD bit is set and the INT bit is a one. No over run or under
run error will be reported when transfers are disabled by INT.

MCE

Mode Change Enable. This bit must be set whenever the current functional mode of the AD1845 is changed
where noted in the Indirect Control Registers 8, 9, 28 and 29. MCE must be cleared at the completion of the
desired register changes.

The DAC outputs are automatically muted when the MCE bit is set. After MCE is cleared, the DAC outputs will
be restored to the state specified by the LDM and RDM mute bits.

Both ADCs and DACs are automatically muted for 32 sample cycles after exiting the MCE state to allow the refer-
ence and all filters to settle. The ADCs will produce midscale values; the DACs' analog output will be muted. All
converters are internally operating during these 32 sample cycles, and the AD1845 will expect playback data and
will generate (midscale) capture data. Note that the autocalibrate-in-progress (ACI) bit will be set on exiting from
the MCE state only when ACAL is set. If ACAL bit is set, ACI will remain HI for these 384 sample cycles, allow-
ing system software to poll this bit rather than count cycles.

Special sequences must be followed if autocalibrate (ACAL) is set during mode change enable. See the
"Autocalibration" section.

INIT

AD1845 Initialization. This bit is set when the AD1845 cannot respond to parallel bus cycles. This bit is
read-only.

Immediately after reset and once the AD1845 has left the INIT state, the initial value of this register will be "0100 0000 (40h)."
During AD1845 initialization, this register cannot be written and always reads "1000 0000 (80h)."

Indexed Data Register (ADR1:0 = 1)

ADR1:0

Data 7

Data 6

Data 5

Data 4

Data 3

Data 2

Data 1

Data 0

IXD7

IXD6

IXD5

IXD4

IXD3

IXD2

IXD1

IXD0

IXD7:0

Indexed Register Data. These bits contain the contents of the AD1845 register referenced by the Indexed Data

During AD1845 initialization, this register cannot be written and always reads as "1000 0000 (80h)."

AD1845

REV. C

Status Register (ADR1:0 = 2)

ADR1:0

Data 7

Data 6

Data 5

Data 4

Data 3

Data 2

Data 1

Data 0

CU/L

CL/R

CRDY

SOUR

PU/L

PL/R

PRDY

INT

Interrupt Status. This sticky bit (the only one) indicates the status of the interrupt logic of the AD1845. This bit
is cleared by any host write of any value to this register. The IEN bit of the Pin Control Register determines
whether the state of this bit is reflected on the INT pin of the AD1845. The only interrupt conditions supported
by the AD1845 are generated by the underflow of the DMA Current Count Register or the Timer Registers. The
Timer Register operates at a 10

s resolution. Clearing INT requires a 10

s wait. If an immediate clearing of a TI

condition is desired, clear the TE bit to remove the timer interrupt.

Interrupt pin inactive

Interrupt pin active

PRDY

Playback Data Register Ready. The PIO or DMA Playback Data Register is ready for more data. This bit is intended
to be used when direct programmed I/O data transfers are desired; however, it is also valid for DMA transfers.
This bit is read-only.

DAC data is still valid. Do not overwrite.

DAC data is stale. Ready for next host data write value.

PL/R

Playback Left/Right Sample. This bit indicates whether the PIO or DMA playback data needed is for the right
channel DAC or left channel DAC. This bit is read-only.

Right channel needed

Left channel or mono

PU/L

Playback Upper/Lower Byte. This bit indicates whether the PIO or DMA playback data needed is for the upper or
lower byte of the channel. This bit is read-only.

Lower byte needed

Upper byte needed or any 8-bit mode

SOUR

Sample Over/Underrun. This bit indicates that the most recent sample was not serviced in time and therefore
either a capture overrun (COR) or playback underrun (PUR) has occurred. The bit indicates an overrun for ADC
capture and an underrun for DAC playback. If both capture and playback are enabled, the source that set this bit
can be determined by reading COR and PUR. This bit changes on a sample by sample basis. This bit is read-only.

CRDY

Capture Data Ready. The PIO Capture Data Register contains data ready for reading by the host. This bit
should only be used when direct programmed I/O data transfers are desired. This bit is read-only.

ADC data is stale. Do not reread the information.

ADC data is fresh. Ready for next host data read.

CL/R

Capture Left/Right Sample. This bit indicates whether the PIO capture data waiting is for the right channel ADC
or left channel ADC. This bit is read-only.

Right channel

Left channel or mono

CU/L

Capture Upper/Lower Byte. This bit indicates whether the PIO capture data ready is for the upper or lower byte
of the channel. This bit is read-only.

Lower byte ready

Upper byte ready or any 8-bit mode

The PRDY, CRDY, and INT bits of this status register can change asynchronously to host accesses. The host may access this regis-
ter while the bits are transitioning. The host read may return a zero value just as these bits are changing, for example. A one value
would not be read until the next host access.

While the FIFOs have multiple samples available for transfer, the CRDY and PRDY status bits for consecutive samples are approxi-
mately 320 ns600 ns apart.

This register's initial state after reset is "1100 1100."

AD1845

REV. C

PIO Data Registers (ADR1:0 = 3)

ADR1:0

Data 7

Data 6

Data 5

Data 4

Data 3

Data 2

Data 1

Data 0

CD7

CD6

CD5

CD4

CD3

CD2

CD1

CD0

PD7

PD6

PD5

PD4

PD3

PD2

PD1

PD0

The PIO Data Registers are two registers mapped to the same address. Writes send data to the PIO Playback Data Register
(PD7:0). Reads will receive data from the PIO Capture Data Register (CD7:0).

During AD1845 initialization, the PIO Playback Data Register cannot be written to and the Capture Data Register is always read
as "1000 0000 (80h)."

CD7:0

PIO Capture Data Register. This is the control register where capture data is read during programmed I/O data
transfers.

The reading of this register will increment the capture byte state machine so that the following read will be from
the next appropriate byte in the sample. The exact byte which is next to be read can be determined by reading the
Status Register. Once all relevant bytes have been read, the state machine will stay pointed to the last byte of the
sample until a new sample is received from the ADCs. Once this has occurred, the state machine and Status
Register will point to the first byte of the sample.

PD7:0

PIO Playback Data Register. This is the control register where playback data is written during programmed I/O
data transfers.

Writing data to this register will increment the playback byte tracking state machine so that the following write will
be to the correct byte of the sample. Once all bytes of a sample have been written, subsequent byte writes to this
port are ignored. The state machine is reset when the current sample is sent to the DACs.

INDIRECT CONTROL REGISTER DEFINITIONS

The following control registers are accessed by writing index values to IXA3:0 in the Index Address Register (ADR1:0 = 0) followed
by a read/write to the Indexed Data Register (ADR1:0 = 1).

Left Input Control (IXA3:0 = 0)

IXA3:0

Data 7

Data 6

Data 5

Data 4

Data 3

Data 2

Data 1

Data 0

LSS1

LSS0

LMGE

res

LIG3

LIG2

LIG1

LIG0

LIG3:0

Left input gain select. The least significant bit of this gain select represents +1.5 dB. Maximum gain is +22.5 dB.

res

Reserved for future expansion. Always write a zero to this bit.

LMGE

Left Input Microphone Gain Enable. This bit will enable the +20 dB gain of the left MIC input signal.

LSS1:0

Left Input Source Select. These bits select the input source for the left gain stage preceding the left ADC.

LSS1

LSS0

Left Input Source

Left Line Source Selected

Left Auxiliary 1 Source Selected

Left Microphone Source Selected

Left Line Post-Mixed DAC Output Source Selected

This register's initial state after reset is "000x 0000."

Right Input Control (IXA3:0 = 1)

IXA3:0

Data 7

Data 6

Data 5

Data 4

Data 3

Data 2

Data 1

Data 0

RSS1

RSS0

RMGE

res

RIG3

RIG2

RIG1

RIG0

RIG3:0

Right Input Gain Select. The least significant bit of this gain select represents +1.5 dB. Maximum gain is +22.5 dB.

res

Reserved for future expansion. Always write a zero to this bit.

RMGE

Right Input Microphone Gain Enable. This bit will enable the +20 dB gain of the right MIC input signal.

RSS1:0

Right Input Source Select. These bits select the input source for the right channel gain stage preceding the right
ADC.

AD1845

REV. C

RSS1

RSS0

Right Input Source

Right Line Source Selected

Right Auxiliary 1 Source Selected

Right Microphone Source Selected

Right Post-Mixed DAC Output Source Selected

This register's initial state after reset is "000x 0000."

Left Auxiliary #1 Input Control (IXA3:0 = 2)

IXA3:0

Data 7

Data 6

Data 5

Data 4

Data 3

Data 2

Data 1

Data 0

LMX1

res

LX1A4

LX1A3

LX1A2

LX1A1

LX1A0

LX1A4:0

Left Auxiliary Input #1 Attenuate Select. The least significant bit of this gain/attenuate select represents 1.5 dB.
LX1A4:0 = 0 produces a +12 dB gain. LX1A4:0 = "01000" (8 decimal) produces 0 dB gain. Maximum attenua-
tion is 34.5 dB. See Figure 10.

res

Reserved for future expansion. Always write zeros to these bits.

LMX1

Left Auxiliary #1 Mute. This bit, when set, will mute the left channel of the Auxiliary #1 input source. This bit
powers up set.

This register's initial state after reset is "1xx0 1000."

Right Auxiliary #1 Input Control (IXA3:0 = 3)

IXA3:0

Data 7

Data 6

Data 5

Data 4

Data 3

Data 2

Data 1

Data 0

RMX1

res

RX1A4

RX1A3

RX1A2

RX1A1

RX1A0

RX1A4:0

Right Auxiliary Input #1 Attenuate Select. The least significant bit of this gain/attenuate select represents
1.5 dB. RX1A4:0 = 0 produces a +12 dB gain. RX1A4:0 = "01000" (8 decimal) produces 0 dB gain. Maximum
attenuation is 34.5 dB. See Figure 10.

res

Reserved for future expansion. Always write zeros to these bits.

RMX1

Right Auxiliary #1 Mute. This bit, when set, will mute the right channel of the Auxiliary #1 input source. This
bit powers up set.

This register's initial state after reset is "1xx0 1000."

Left Auxiliary #2 Input Control (IXA3:0 = 4)

IXA3:0

Data 7

Data 6

Data 5

Data 4

Data 3

Data 2

Data 1

Data 0

LMX2

res

LX2A4

LX2A3

LX2A2

LX2A1

LX2A0

LX2A4:0

Left Auxiliary Input #2 Attenuate Select. The least significant bit of this gain/attenuate select represents 1.5 dB.
LX2A4:0 = 0 produces a +12 dB gain. LX2A4:0 = "01000" (8 decimal) produces 0 dB gain. Maximum attenua-
tion is 34.5 dB. See Figure 10.

res

Reserved for future expansion. Always write zeros to these bits.

LMX2

Left Auxiliary #2 Mute. This bit, when set to 1, will mute the left channel of the Auxiliary #2 input source. This
bit powers up set.

This register's initial state after reset is "1xx0 1000."

Right Auxiliary #2 Input Control (IXA3:0 = 5)

IXA3:0

Data 7

Data 6

Data 5

Data 4

Data 3

Data 2

Data 1

Data 0

RMX2

res

RX2A4

RX2A3

RX2A2

RX2A1

RX2A0

AD1845

REV. C

RX2A4:0

Right Auxiliary Input #2 Attenuate Select. The least significant bit of this gain/attenuate select represents
1.5 dB. RX2A4:0 = 0 produces a +12 dB gain. RX2A4:0 = "01000" (8 decimal) produces 0 dB gain.
Maximum attenuation is 34.5 dB. See Figure 10.

res

Reserved for future expansion. Always write zeros to these bits.

RMX2

Right Auxiliary #2 Mute. This bit, when set, will mute the right channel of the Auxiliary #2 input source. This bit
powers up set.

This register's initial state after reset is "1xx0 1000."

Left DAC Control (IXA3:0 = 6)

IXA3:0

Data 7

Data 6

Data 5

Data 4

Data 3

Data 2

Data 1

Data 0

LDM

res

LDA5

LDA4

LDA3

LDA2

LDA1

LDA0

LDA5:0

Left DAC Attenuate Select. The least significant bit of this gain/attenuate select represents 1.5 dB. Maximum
attenuation is 94.5 dB. See Figure 7.

res

Reserved for future expansion. Always write a zero to this bit.

LDM

Left DAC Mute. This bit, when set to 1, will mute the left DAC output. This bit powers up active.

This register's initial state after reset is "1x00 0000."

Right DAC Control (IXA3:0 = 7)

IXA3:0

Data 7

Data 6

Data 5

Data 4

Data 3

Data 2

Data 1

Data 0

RDM

res

RDA5

RDA4

RDA3

RDA2

RDA1

RDA0

RDA5:0

Right DAC Attenuate Select. The least significant bit of this gain/attenuate select represents 1.5 dB. Maximum
attenuation is 94.5 dB. See Figure 7.

res

Reserved for future expansion. Always write a zero to this bit.

RDM

Right DAC Mute. This bit, when set to 1, will mute the right DAC output. This bit powers up active.

This register's initial state after reset is "1x00 0000."

Mix Gain

11.

0 dB

1.5 dB

3.0 dB

4.5 dB

6.0 dB

7.5 dB

9.0 dB

10.5 dB

12.0 dB

13.5 dB

15.0 dB

16.5 dB

78.0 dB

79.5 dB

81.0 dB

82.5 dB

84.0 dB

85.5 dB

87.0 dB

88.5 dB

90.0 dB

91.5 dB

93.0 dB

94.5 dB

Figure 7. Mix Gain Level Setting: DAC

AD1845

REV. C

Clock and Data Format Register (IXA3:0 = 8)

IXA3:0

Data 7

Data 6

Data 5

Data 4

Data 3

Data 2

Data 1

Data 0

FMT1

FMT0

C/L

S/M

CFS2

CFS1

CFS0

CSS

NOTE: Placing the AD1845 in the Mode Change Enable (MCE) state is not required when changing the sample rate. However,
changes to FMT[1:0], C/L, and S/M require MCE or setting PEN = 0.

CSS

Clock Source Select. This bit in conjunction with CFS2:0 selects the audio sample rate frequency. See Figure 8
below. Note: MODE2 allows a wider range of sample rate frequencies to be selected by using the Frequency
Select Register (refer to Registers 22 and 23).

CFS2:0

Clock Frequency Divide Select. These bits in conjunction with CSS select the audio sample frequency.

CFS2

CFS1

CFS0

CSS

Sample Rate

8.0

kHz

5.5125

kHz

16.0

kHz

11.025

kHz

27.42857 kHz

18.9

kHz

32.0

kHz

22.05

kHz

Reserved

37.8

kHz

Reserved

44.1

kHz

48.0

kHz

33.075

kHz

9.6

kHz

6.615

kHz

Figure 8. MODE1 Audio Sample Frequency Select

S/M

Stereo/Mono Select. This bit determines how the audio data streams are formatted. Selecting stereo will result
with alternating samples representing left and right audio channels. Mono playback plays the same audio sample
on both channels. Mono capture only captures data from the left audio channel.

Mono

Stereo

C/L

Companded/Linear Select. This bit selects between a linear digital representation of the audio signal or a nonlinear,
companded format for all input and output data. The type of linear PCM or the type of companded format is
defined by the FMT bits.

Linear PCM

Companded

FMT[1:0]

Format Select. The bits define the format for all digital audio input and outputs based on the state of the C/L bit.
See Figure 9 for FMT and C/L bit settings that determine the audio data type format.

res

Reserved for future expansion. Always write a zero to this bit.

This register's initial state after reset is "0000 0000."

FMT1

FMT0

C/L

Audio Data Type

Linear, 8-Bit Unsigned PCM

-Law, 8-Bit Companded

Linear, 16-Bit Twos-Complement PCM Little Endian

A-Law, 8-Bit Companded

Reserved

Linear, 16-Bit Twos Complement Big Endian

Reserved

Figure 9. Digital Audio Data Type

AD1845

REV. C

Interface Configuration Register (IXA3:0 = 9)

IXA3:0

Data 7

Data 6

Data 5

Data 4

Data 3

Data 2

Data 1

Data 0

CPIO

PPIO

res

ACAL

SDC

CEN

PEN

NOTE: Placing the AD1845 in the Mode Change Enable (MCE) state is not required when changing the CEN and PEN bits in this
register.

PEN

Playback Enable. This bit will enable the playback of data in the format selected. The AD1845 will generate
PDRQ and respond to

PDAK signals when this bit is enabled and PPIO = 0. If PPIO = 1, this bit enables Pro-

grammed I/O (PIO) playback mode.

Playback disabled (PDRQ and PIO Playback Data Register inactive)

Playback enabled

CEN

Capture Enable. This bit will enable the capture of data in the format selected. The AD1845 will generate
CDRQ and respond to

CDAK signals when this bit is enabled and CPIO = 0. If CPIO = 1, this bit enables PIO

capture mode.

Capture disable (CDRQ and PIO Capture Data Register inactive)

Capture enable

SDC

Single DMA Channel. This bit will force both capture and playback DMA requests to occur on the Playback
DMA channel. The Capture DMA CDRQ pin will be LO. This bit will allow the AD1845 to be used with only
one DMA channel. Simultaneous capture and playback cannot occur in this mode. Should both capture and
playback be enabled (CEN=PEN=1) in the mode, only playback will occur. See "Data and Control Transfers" for
further explanation.

Dual DMA channel mode

Single DMA channel mode

ACAL

Autocalibrate Enable. This bit determines whether the AD1845 performs an autocalibration whenever the Mode
Change Enable (MCE) bit changes from HI to LO. See "Autocalibration" for a description of a complete
autocalibration sequence. Note that an autocalibration is forced whenever the

RESET or PWRDWN pin is

asserted LO then transitions HI regardless of the state of the ACAL bit.

No autocalibration

Autocalibration after mode change

res

Reserved for future expansion. Always write zeros to these bits.

PPIO

Playback PIO Enable. This bit determines whether the playback data is transferred via DMA or PIO.

DMA transfers only

PIO transfers only

CPIO

Capture PIO Enable. This bit determines whether the capture data is transferred via DMA or PIO.

DMA transfers only

PIO transfers only

This register's initial state after reset is "00xx 1000."

Pin Control Register (IXA3:0 = 10)

IXA3:0

Data 7

Data 6

Data 5

Data 4

Data 3

Data 2

Data 1

Data 0

XCTL1

XCTL0

res

IEN

INITD

Disable setting the INIT bit after changing the sample rate in MODE1. Otherwise the INIT bit is set HI for
approximately 200

s after changing the sample rate.

INIT bit is enabled

INIT bit is disabled

IEN

Interrupt Enable. This bit enables the interrupt pin. The Interrupt Pin will go active HI when the number of
samples programmed in the Base Count Register is reached.

Interrupt disabled

Interrupt enabled

res

Reserved for future expansion. Always write zeros to these bits.

AD1845

REV. C

XCTL1:0

External Control. The state of these bits is reflected on the XCTL1:0 pins of the AD1845.
0

Logic LO on XCTL1:0 pins

Logic HI on XCTL1:0 pins

This register's initial state after reset is "00xx xx00."

Test and Initialization Register (IXA3:0 = 11)

IXA3:0

Data 7

Data 6

Data 5

Data 4

Data 3

Data 2

Data 1

Data 0

COR

PUR

ACI

DRS

ORR1

ORR0

ORL1

ORL0

ORL1:0

Overrange Left Detect. These bits indicate the overrange on the left capture channel. These bits change on
a sample-by-sample basis, and are read-only.

ORL1

ORL0

Less than 1 dB underrange

Between 1 dB and 0 dB underrange

Between 0 dB and +1 dB overrange

Greater than +1 dB overrange

ORR1:0

Overrange Right Detect. These bits indicate the overrange on the right capture channel. These bits change
on a sample-by-sample basis, and are read-only.

ORR1

ORR0

Less than 1 dB underrange

Between 1 dB and 0 dB underrange

Between 0 dB and +1 dB overrange

Greater than +1 dB overrange

DRS

Data Request Status. This bit indicates the current status of the PDRQ and CDRQ pins of the AD1845.

CDRQ and PDRQ are presently inactive (LO)

CDRQ or PDRQ are presently active (HI)

ACI

Autocalibrate-In-Progress. This bit indicates the state of autocalibration or a recent exit from Mode Change
Enable (MCE). This bit is read-only.

Autocalibration is not in progress

Autocalibration is in progress or MCE was exited within the last 128 sample periods

PUR

Playback Underrun. This bit is set when the playback FIFO is empty and after the next valid sample has been
played back. If this condition exists, DACZ determines the DAC playback value. In MODE1, DACZ is always set
and returns a midscale value.

COR

Capture Overrun. This bit is set when the capture FIFO is full and an additional sample has been captured. The
sample being read will not be overwritten by the new sample. The new sample will be ignored. This bit changes on
a sample by sample basis.

The occurrence of a PUR and/or COR is designated in the Status Register's Sample Overrun/Underrun (SOUR) bit. The SOUR bit
is the logical OR of the COR and PUR bits. This enables a polling host CPU to detect an overrun/underrun condition while check-
ing other status bits.

This register's initial state after reset is "0000 0000."

Miscellaneous Control Register (IXA3:0 = 12)

IXA3:0

Data 7

Data 6

Data 5

Data 4

Data 3

Data 2

Data 1

Data 0

MID

MODE2

res

BUF8

ID3

ID2

ID1

ID0

ID3:0

AD1845 Revision ID. These four bits define the revision level of the AD1845. The AD1845 will have ID =
"1010." These bits are read-only.

BUF8

Parallel Interface Bus Transceiver Current Buffer Drive. The AD1845 can be programmed to provide a current
drive of 16 mA or 8 mA.

16 mA current drive.

8 mA current drive.

res

Reserved for future expansion. Always write 0s to these bits.

AD1845

REV. C

MODE2

When the AD1845 is initialized, the MODE2 bit is set to 0, LO, and the AD1845 is register set compatible with
the AD1848 and the AD1846. Setting the MODE2 bit to 1, HI, enables access to the indirect registers 16
through 31 which controls the AD1845 Expanded Mode of operation.

MODE1: AD1848, AD1846, and CS4248 mode

MODE2: AD1845 enhanced feature mode

MID

Manufacturer ID Bit. This bit is set to 1.

This register's initial state after reset is "10x0 1010."

Digital Mix/Attenuation Control Register (IXA3:0 = 13)

IXA3:0

Data 7

Data 6

Data 5

Data 4

Data 3

Data 2

Data 1

Data 0

DMA5

DMA4

DMA3

DMA2

DMA1

DMA0

res

DME

Digital Mix Enable. This bit will enable the digital mix of the ADC's output with the DAC's input. When en-
abled, the data from the ADCs are digitally mixed with other data being delivered to the DACs regardless of
whether or not playback is enabled (PEN = 1). If capture is enabled (CEN = 1) and there is a capture overrun
(COR), then the last sample captured before overrun will be used for the digital mix. If playback is enabled
(PEN = 1) and there is a playback underrun (PUR), then a midscale zero will be added to the digital mix data if
DACZ = 1, otherwise, the last valid sample will be repeated.

Digital mix disabled (muted)

Digital mix enabled

res

Reserved for future expansion. Always write a zero to this bit.

DMA5:0

Digital Mix Attenuation. These bits determine the attenuation of the ADC data that is mixed with the DAC in-
put. Each attenuate step is 1.5 dB ranging from 0 dB to 94.5 dB.

This register's initial state after reset is "0000 00x0."

DMA Playback Base Count Registers (IXA3:0 = 14 & 15)

The DMA Base Count Registers in the AD1845 simplify integration of the AD1845 in ISA systems. The ISA DMA controller re-
quires an external count mechanism to notify the host CPU via interrupt of a full DMA buffer. The programmable DMA Base
Count Registers will allow such interrupts to occur.

The Base Count Registers contain the number of samples to be transferred before an interrupt is generated on the interrupt (INT)
pin. To load, first write a value to the Lower Base Count Register. Writing a value to the Upper Base Register will cause both Base
Count Registers to load into the Current Count Register. Once AD1845 transfers are enabled, each sample transferred causes the
Current Count Register to decrement until zero count is reached. The next sample after zero will generate the interrupt and reload
the Current Count Register with the values in the Base Count Registers. The interrupt is cleared by a write to the Status Register.

The Host Interrupt Pin (INT) will go HI during the sample period in which the Current Count Register underflows.

When using the AD1845 in MODE1 (AD1848 compatible), the Current Count Register is decremented every sample period when
either the PEN or CEN bit is enabled. The Current Count Register is decremented in both PIO and DMA data transfer modes.
Interrupt conditions are generated by Current Count Register underflows in both PIO and DMA transfers.

Program maximum value to the Upper Base Count Register to avoid receiving DMA count interrupts while operating in PIO mode.
By enabling MODE2, the AD1845 Expanded Mode, the playback counter is only decremented when a playback sample transfer occurs.

Upper Base Count Register (IXA3:0 = 14)

IXA3:0

Data 7

Data 6

Data 5

Data 4

Data 3

Data 2

Data 1

Data 0

UB7

UB6

UB5

UB4

UB3

UB2

UB1

UB0

UB7:0

Upper Base Count. This byte is the upper byte of the base count register containing the eight most significant bits
of the 16-bit base register. Reads from this register return the same value which was written. The current count
contained in the counters can not be read.

This register's initial state after reset is " 0000 0000."

AD1845

REV. C

Lower Base Count Register (IXA3:0 = 15)

IXA3:0

Data 7

Data 6

Data 5

Data 4

Data 3

Data 2

Data 1

Data 0

LB7

LB6

LB5

LB4

LB3

LB2

LB1

LB0

LB7:0

Lower Base Count. This byte is the lower byte of the base count register containing the eight least significant bits
of the 16-bit base register. Reads from this register return the same value which was written. The current count
contained in the counters cannot be read.

This register's initial state after reset is "0000 0000."

Expanded Modes (MODE2 = 1)

The following registers are enabled when the AD1845 is operating in MODE2 only.

Alternate Feature Enable/Left MIC Input Control Register (IXA3:0 = 16)

IXA3:0

Data 7

Data 6

Data 5

Data 4

Data 3

Data 2

Data 1

Data 0

LMG4

LMG3

LMG2

LMG1

LMG0

DACZ

DAC Zero. When an underrun error occurs, this bit will force the DAC output to midscale.

Output previous valid sample

Output to midscale value

LMG4:0

Left MIC Gain. The least significant bit of this gain/attenuate select represents 1.5 dB. LMG4:0 = 0 produces
a +12 dB gain. LMG4:0 = "01000" (8 decimal) produces 0 dB gain. Maximum attenuation is 34.5 dB.
See Figure 10.

Timer Enable. Setting this bit enables the 16-bit programmable timer (see Registers 20 and 21). When the timer
is enabled, the timer count is reloaded, and interrupts are generated at specified periods on the INT pin. When the
timer is disabled, the timer stops counting and the INT pin and TI bit are cleared immediately.

Output Level. This bit sets the analog output level. The line output level may be attenuated by 3 dB.

Full scale of 2.0 V p-p (3 dB)

Full scale of 2.8 V p-p (0 dB)

This register's initial state after reset is "0001 0001."

MIC Mix Enable/Right MIC Input Control Register (IXA3:0 = 17)

IXA3:0

Data 7

Data 6

Data 5

Data 4

Data 3

Data 2

Data 1

Data 0

LMME

RMME

RMG4

RMG3

RMG2

RMG1

RMG0

res

Reserved for future expansion. Always write zero to this bit.

RMG4:0

Right MIC Gain. The least significant bit of this gain/attenuate select represents 1.5 dB. RMG4:0 = 0 produces a
+12 dB gain. RMG4:0 = "01000" (8 decimal) produces 0 dB gain. Maximum attenuation is 34.5 dB.
See Figure 10.

RMME

Right MIC Mix Enable. Setting this bit enables the right microphone input to be mixed with the DAC output on
R_OUT.

LMME

Left MIC Mix Enable. Setting this bit enables the left microphone input to be mixed with the DAC output on
L_OUT.

This register's initial state after reset is "0001 000x."

Left Line Gain, Attenuate, Mute Mix Register (IXA3:0 = 18)

IXA3:0

Data 7

Data 6

Data 5

Data 4

Data 3

Data 2

Data 1

Data 0

LLM

res

LLG4

LLG3

LLG2

LLG1

LLG0

LLG4:0

Left Line Mix Gain. Allows setting the left line mix gain in thirty-two 1.5 dB steps. See Figure 10 for mix gain
level setting.

res

Reserved for future expansion. Always write zeros to these bits.

AD1845

REV. C

LLM

Left Line Mute. Setting this bit to 1 mutes the left line input into the output mixer.

This register's initial state after reset is "1xx0 1000."

Right Line Gain, Attenuate, Mute, Mix Register (IXA3:0 = 19)

IXA3:0

Data 7

Data 6

Data 5

Data 4

Data 3

Data 2

Data 1

Data 0

RLM

res

RLG4

RLG3

RLG2

RLG1

RLG0

RLG4:0

Right Line Mix Gain. Allows setting the right line mix gain in thirty-two 1.5 dB steps. See Figure 10 for mix
gain level setting.

res

Reserved for future expansion. Always write zeros to these bits.

RLM

Right Line Mute. Setting this bit to 1 mutes the right line input into the output mixer.

This register's initial state after reset is "1xx0 1000."

A4/G4

A3/G3

A2/G2

A1/G1

A0/G0

Mix Gain

+12.0 dB

+10.5 dB

+9.0 dB

+7.5 dB

+6.0 dB

+4.5 dB

+3.0 dB

+1.5 dB

+0.0 dB

1.5 dB

3.0 dB

4.5 dB

6.0 dB

7.5 dB

9.0 dB

10.5 dB

12.0 dB

13.5 dB

15.0 dB

16.5 dB

18.0 dB

19.5 dB

21.0 dB

22.5 dB

24.0 dB

25.5 dB

27.0 dB

28.5 dB

30.0 dB

31.5 dB

33.0 dB

34.5 dB

Figure 10. Mix Gain Level Setting: AUX1, AUX2, MIC and LINE

Lower Timer Bits Register (IXA3:0 = 20)

IXA3:0

Data 7

Data 6

Data 5

Data 4

Data 3

Data 2

Data 1

Data 0

TL7

TL6

TL5

TL4

TL3

TL2

TL1

TL0

TL7:0

Lower Timer Bits. This byte is the lower byte of the timer register containing the eight least significant bits of the
16-bit register. Reads from this register return the same value which was written. The current timer value con-
tained in the counters cannot be read.

This register's initial state after reset is "0000 0000."

AD1845

REV. C

Upper Timer Bits Register (IXA3:0 = 21)

IXA3:0

Data 7

Data 6

Data 5

Data 4

Data 3

Data 2

Data 1

Data 0

TU7

TU6

TU5

TU4

TU3

TU2

TU1

TU0

TU7:0

Upper Timer Bits. This byte is the upper byte of the timer register containing the eight most significant bits of the
16-bit register. Reads from this register return the same value which was written. The current timer value con-
tained in the counters cannot be read. The timer counter is determined by the clock source selected (see below).

Input Frequency

Divider

Timer Counter

24.576 MHz

247

10.050

14.31818 MHz

144

10.057

24.000 MHz

242

10.083

25.000 MHz

252

10.080

33.000 MHz

333

10.091

This register's initial state after reset is "0000 0000."

Upper Frequency Select Bits Register (IXA3:0 = 22)

IXA3:0

Data 7

Data 6

Data 5

Data 4

Data 3

Data 2

Data 1

Data 0

FU7

FU6

FU5

FU4

FU3

FU2

FU1

FU0

FU7:0

Upper Frequency Select Bits. This register is accessible when FREN is 1. Writing to this register allows the user
to program the sampling frequency from 4 kHz to 50 kHz in 1 Hz increments. Writing to the Lower and Upper
Frequency Select Register allows the AD1845 to process audio data using approximately 50,000 different audio
sample rates. One LSB represents exactly one hertz. Selecting frequencies below 4 kHz or above 50 kHz will
result in degraded audio performance. Some common sample rates are listed below:

Quality

Sampling Frequency

FU7:0 (hex)

FL7:0 (hex)

Voice

8.0 kHz

0001 1111

0100 0000

default

Radio

11.025 kHz

0010 1011

0001 0001

Tape

22.05 kHz

0101 0110

0010 0010

44.1 kHz

1010 1100

0100 0100

DAT

48.0 kHz

1011 1011

1000 0000

This register's initial state after reset is "0001 1111."

Lower Frequency Select Bits Register (IXA3:0 = 23)

IXA3:0

Data 7

Data 6

Data 5

Data 4

Data 3

Data 2

Data 1

Data 0

FL7

FL6

FL5

FL4

FL3

FL2

FL1

FL0

FL7:0

Lower Frequency Select Bits. Writing to the Lower Frequency Select register updates the entire 16-bit frequency register.

This register's initial state after reset is "0100 0000."

Capture Playback Timer Register (IXA3:0 = 24)

IXA3:0

Data 7

Data 6

Data 5

Data 4

Data 3

Data 2

Data 1

Data 0

res

Playback Underrun. This bit is set when the DAC runs out of data and a sample has been missed.

Playback Overrun. This bit is set when the host tries to write data into the FIFO and the write was ignored be-
cause the FIFO was full.

Capture Overrun. This bit is set when the ADC has a sample to load into the FIFO, and the data was ignored
because the capture FIFO was full.

Capture Underrun. This bit is set when the host attempts to read from the capture FIFO when it is empty. Under
these circumstances, the last valid byte is sent to the host.

Playback Interrupt. This bit indicates that there is an interrupt pending from the playback DMA count registers.

Capture Interrupt. This bit indicates that there is an interrupt pending from the capture DMA count registers.

AD1845

REV. C

Timer Interrupt. This bit indicates that there is an interrupt pending from the timer count registers.

res

Reserved for future expansion. Always write zero to this bit.

Playback, Capture and timer interrupts may be cleared simultaneously by writing to the Status Register. These interrupts may be
cleared individually by writing a "0" to the corresponding bit. Note that the timer interrupt requires a minimum wait period of 10

after the interrupt is set and before TI is recognized. Use TE to clear the timer interrupt immediately.

This register's initial state after reset is "100x x000."

Revision ID Register (IXA3:0 = 25)

IXA3:0

Data 7

Data 6

Data 5

Data 4

Data 3

Data 2

Data 1

Data 0

res

CID2

CID1

CID0

V2:0

Version Number. Indicates the version of the AD1845.

res

Reserved for future expansion. Always write zeros to these bits.

CID2:0

Chip ID Number.

This register's initial state after reset is "x000 0000."

Mono Control Registers (IXA3:0 = 26)

IXA3:0

Data 7

Data 6

Data 5

Data 4

Data 3

Data 2

Data 1

Data 0

MIM

MOM

res

MIA3

MIA2

MIA1

MIA0

MIA3:0

Mono Input Attenuation. The least significant bit represents 3.0 dB attenuation. See Figure 11 to determine
the attenuation.

res

Reserved for future expansion. Always write zeros to these bits.

MOM

Mono Output Mute. M_OUT is muted by setting MOM to 1.

Mono output not muted

Mono output muted

MIM

Mono Input Mute. M_IN is muted by setting MIM to 1.

Mono input not muted

Mono input muted

This register's initial state after reset is "00xx 0011."

MIA3

MIA2

MIA1

MIA0

MONO Attenuation

0.0 dB

3.0 dB

6.0 dB

9.0 dB

12.0 dB

15.0 dB

18.0 dB

21.0 dB

24.0 dB

27.0 dB

30.0 dB

33.0 dB

36.0 dB

39.0 dB

42.0 dB

45.0 dB

Figure 11. Mono Attenuation

AD1845

REV. C

Power-Down Control Register (IXA3:0 = 27)

IXA3:0

Data 7

Data 6

Data 5

Data 4

Data 3

Data 2

Data 1

Data 0

ADCPWD

DACPWD

MIXPWD

res

FREN

res

Reserved for future expansion. Always write zeros to these bits.

FREN

Frequency Select Register Enable. In MODE2, selecting this bit will turn on the Frequency Select Registers (see
indirect registers 22 and 23) and disable CFS2:0.

CFS Active.

Frequency Select Registers Active, CFS disabled.

MIXPWD

Mixer Power Down. The DAC and the output mixer are powered down, and the DAC sample clock is turned off.

DACPWD

DAC Power Down. The DAC is powered down and the DAC sample clock is turned off.

ADCPWD

ADC Power Down. The ADC is powered down and the ADC sample clock is turned off.

This register's initial state after reset is "000x 0xxx."

Capture Data Format Control Register (IXA3:0 = 28)

IXA3:0

Data 7

Data 6

Data 5

Data 4

Data 3

Data 2

Data 1

Data 0

CFMT1

CFMT0

CC/L

CS/M

res

NOTE: Changing CFMT[1:0], CC/L, CS/M, requires the Mode Change Enable (MCE) state or setting CEN = 0.

res

Reserved for future expansion. Always write zeros to these bits.

CS/M

Capture Stereo/Mono Select. Setting this bit determines how the captured audio data will be formatted. In the
Mono mode, valid information is captured on the "left" channel, and the "right" channel data is not valid.

Mono Format

Stereo Format

CC/L

Capture Companding/Linear Select. This bit is set to determine linear,

-Law or A-Law companding. See Figure

12 for CFMT[1:0] and CC/L bit settings that determine the audio data type capture format.

CFMT[1:0]

Capture Data Format. This bit is set to format the data being captured in MODE 2. See Figure 12 for CFMT
and CC/L bit settings that determine the capture audio data type format.

This register's initial state after reset is "0000 xxxx."

CFMT1

CFMT0

CC/L

Audio Data Type

Linear, 8-Bit Unsigned PCM

-Law, 8-Bit Companded

Linear, 16-Bit Twos Complement PCM Little Endian

A-Law, 8-Bit Companded

Reserved

Linear, 16-Bit Twos-Complement Big Endian

Reserved

Figure 12. Capture Audio Data Type

Crystal, Clock Select/Total Power-Down Register (IXA3:0 = 29)

IXA3:0

Data 7

Data 6

Data 5

Data 4

Data 3

Data 2

Data 1

Data 0

XFS2

XFS1

XFS0

res

TOTPWD

Total Power Down. When TOTPWD = HI, the ADC, DAC, mixer, and voltage reference are powered down, and
the ADC and DAC sample clocks are turned off. Only the digital interface remains active to allow the host to exit
the AD1845 from the total power-down state.

res

Reserved for future expansion. Always write zeros to these bits.

AD1845

REV. C

XFS2:0

Crystal/Clock Input Frequency Select. On power up or reset, the AD1845 expects a 24.576 MHz input clock. If
the clock source connected to the AD1845 is different from the default condition, then the clock input must be
selected using this register. For a detailed explanation see the Power Up and Reset section of the data sheet. Figure
13 summarizes the valid input clock frequencies. Clock sources with excessive jitter may not yield optimal analog
performance.

This register's initial state after reset is "000x xxx0."

XFS2

XFS1

XFS0

Input Frequency

24.576

MHz

14.31818 MHz

24.000

MHz

25.000

MHz

33.000

MHz

Reserved

Figure 13. Input Frequency Selection

Capture Upper Base Count Register (IXA3:0 = 30)

IXA3:0

Data 7

Data 6

Data 5

Data 4

Data 3

Data 2

Data 1

Data 0

CUB7

CUB6

CUB5

CUB4

CUB3

CUB2

CUB1

CUB0

CUB7:0

Capture Upper Base Count. This byte is the upper byte of the base count register containing the eight most sig-
nificant bits of the second 16-bit base register. Reads from this register return the same value that was written.
The current count contained in the counters cannot be read.

This register's initial state after reset is "0000 0000."

Capture Lower Base Count Register (IXA3:0 = 31)

IXA3:0

Data 7

Data 6

Data 5

Data 4

Data 3

Data 2

Data 1

Data 0

CLB7

CLB6

CLB5

CLB4

CLB3

CLB2

CLB1

CLB0

CLB7:0

Capture Lower Base Count. This byte is the lower byte of the base count register containing the eight least signifi-
cant bits of the second 16-bit base register. Reads from this register return the same value that was written. The
current count contained in the counters cannot be read.

This register's initial state after reset is "0000 0000."

AD1845

REV. C

DATA AND CONTROL TRANSFERS

Data Ordering

The number of byte-wide transfers required depends on the
data format selected. The AD1845 is designed for "little and
big endian" formats. In little endian format, the least significant
byte (i.e., occupying the lowest memory address) gets trans-
ferred first. Therefore, 16-bit data transfers require first trans-
ferring the least significant bits [7:0] and then transferring the
most significant bits [15:8], where Bit 15 is the most significant
bit in the word. In big endian format, byte ordering for the most
significant (MS) byte and least significant (LS) byte are swapped.

In addition, left channel data is always transferred before right
channel data with the AD1845. The following figures should
make these requirements clear.

SAMPLE 6 SAMPLE 5 SAMPLE 4 SAMPLE 3 SAMPLE 2 SAMPLE 1

BYTE 4 BYTE 3 BYTE 2 BYTE 1

TIME

MONO MONO MONO MONO

Figure 14. 8-Bit Mono Data Stream Sequencing

BYTE 4 BYTE 3 BYTE 2 BYTE 1

TIME

SAMPLE 3 SAMPLE 3 SAMPLE 2 SAMPLE 2 SAMPLE 1 SAMPLE 1

RIGHT LEFT

Figure 15. 8-Bit Stereo Data Stream Sequencing

BYTES 3 AND 4 BYTES 1 AND 2

SAMPLE 6 SAMPLE 5 SAMPLE 4 SAMPLE 3 SAMPLE 2 SAMPLE 1

TIME

Figure 16. 16-Bit Mono Data Stream Sequencing, Little
Endian

BYTES 3 AND 4 BYTES 1 AND 2

TIME

SAMPLE 3 SAMPLE 3 SAMPLE 2 SAMPLE 2 SAMPLE 1 SAMPLE 1

RIGHT MS RIGHT LS

LEFT MS

LEFT LS

Figure 17. 16-Bit Stereo Data Stream Sequencing, Little
Endian

BYTES 3 AND 4 BYTES 1 AND 2

TIME

SAMPLE 6 SAMPLE 5 SAMPLE 4

SAMPLE 4

SAMPLE 3

SAMPLE 2 SAMPLE 1

Figure 18. 16-Bit Mono Data Stream Sequencing, Big
Endian

BYTES 3 AND 4 BYTES 1 AND 2

TIME

SAMPLE 3 SAMPLE 3 SAMPLE 2 SAMPLE 2 SAMPLE 1 SAMPLE 1

RIGHT LS RIGHT MS

LEFT LS

LEFT MS

Figure 19. 16-Bit Stereo Data Stream Sequencing, Big
Endian

FIFO

The AD1845 includes two 16-sample deep FIFOs. The FIFOs
are built into the capture and playback paths and are completely
transparent to the user and require no programming. The
FIFOs are active in MODE1 and MODE2.

The AD1845 maintains a continuous playback stream by re-
questing data from the host until the FIFO located in the play-
back path is full. As the FIFO empties, new samples are
requested to keep the playback FIFO full. In the event that the
FIFO runs out of data and DACZ is reset to "0," the last valid
sample will be continuously played back. If DACZ is "1," the
AD1845 will output a midscale value.

The FIFO located in the capture data path attempts to stay
empty by making requests of the host every sample period that it
contains valid data. When the host system cannot respond
during the same sample period, the capture FIFO starts filling,
and avoids a loss of data in the audio data stream.

Data Bus Drivers

The AD1845 has built-in 8 or 16 mA bus drivers for interfacing
to the ISA bus. The drivers reduce the need for the off-chip
74_245 bus transceiver buffers in many applications. If higher
drive capability is required, 24 mA for example, the AD1845
generates the appropriate direction and enable signals. See
Figure 1 and refer to the Applications Circuits section of the
data sheet.

Control and Programmed I/O (PIO) Transfers

This simpler mode of transfers is used both for control register
accesses and programmed I/O. The 37 control and PIO data
registers cannot be accessed via DMA transfers. Playback PIO

AD1845

REV. C

is activated when both Playback Enable (PEN) is set and Play-
back PIO (PPIO) is set. Capture PIO is activated when both
Capture Enable (CEN) is set and Capture PIO (CPIO) is set.
See Figures 20 and 21 for the detailed timing of the control
register/PIO transfers. The

RD and WR signals are used to

define the actual read and write cycles, respectively. The host
holds

CS LO during these transfers. The DMA Capture Data

Acknowledge (

CDAK) and Playback Data Acknowledge

(

PDAK) must be held inactive, i.e., HI.

For read/capture cycles, the AD1845 will place data on the
DATA7:0 lines while the host is asserting the read strobe,

RD,

by holding it LO. For write/playback, the host must place data
on the DATA7:0 pins while strobing the

WR signal LO. The

AD1845 latches the write/playback data on the rising edge of
the

WR strobe.

When using PIO data transfers, the Status Register must be
polled to determine when data should be transferred. Note that
the ADC capture data will be ready (CRDY HI) from the previ-
ous sample period shortly before the DAC playback data is
ready (PRDY HI) for the next sample period. The user should
not wait for both ADCs and DACs to become ready before
initiating data transfers. Instead, as soon as capture data is
ready, it should be read; as soon as the DACs are ready, play-
back data should be written.

Values written to the XCTL1:0 bits in the Pin Control Register
(IXA3:0 = 10) will be reflected in the state of the XCTL1:0
external output pins. This feature allows a simple method for
signaling or software control of external logic. Changes in state
of the external XCTL pins will occur within one sample period.
Because their change is referenced to the internal sample clock,
no useful timing diagram can be constructed.

DIRECT MEMORY ACCESS (DMA) TRANSFERS

The second type of bus cycle supported by the AD1845 are
DMA transfers. Both dual channel and single channel DMA
operations are supported. To enable Playback DMA transfers,
playback enable (PEN) must be set and PPIO cleared. To
enable Capture DMA transfers, capture enable (CEN) must be
set and CPIO cleared. During DMA transfers, the AD1845
asserts HI the Capture Data Request (CDRQ) or the Playback
Data Request (PDRQ) followed by the host's asserting LO
the DMA Capture Data Acknowledge (

CDAK) or Playback

Data Acknowledge (

PDAK), respectively. The host's asserted

CDRQ/PDRQ

OUTPUTS

ADSU

ADHD

DHD1

RDDV

STW

DBDL

CSSU

CSHD

SUDK1

SUDK2

CDAK

INPUT

DBEN

& DBDIR

OUTPUTS

INPUT

DATA7:0

OUTPUTS

DATA1:0

INPUTS

Figure 20. Control Register/PIO Read Cycle

CDRQ/PDRQ

OUTPUTS

ADSU

ADHD

DHD2

DBDL

CSSU

CSHD

PDAK

INPUT

DBEN

OUTPUT

INPUT

DATA7:0

INPUTS

DATA1:0

INPUTS

WDSU

DBDIR OUTPUT

SUDK2

STW

SUDK1

Figure 21. Control Register/PIO Write Cycle

Acknowledge signals cause the AD1845 to perform DMA trans-
fers. The input address lines, ADR1:0, are ignored. Data is
transferred between the proper internal sample registers.

The read strobe (

RD) and write strobe (WR) delimit valid data

for DMA transfers. Chip select (

CS) is a "don't care"; its state

is ignored by the AD1845.

The AD1845 may assert the Data Request signals, CDRQ and
PDRQ, at any time. Once asserted, these signals will remain
active HI until the corresponding DMA cycle occurs with the
host's Data Acknowledge signals. The Data Request signals will
be deasserted after the falling edge of the final

RD or WR strobe

in the transfer of a sample, which typically consists of multiple
bytes. See "Data Ordering" above for a definition of "sample."

DMA transfers may be independently aborted by resetting the
Capture Enable (CEN) and/or Playback Enable (PEN) bits in
the Interface Configuration Register. The current capture
sample transfer will be completed if a capture DMA is termi-
nated. The current playback sample transfer must be completed
if a playback DMA is terminated. If CDRQ and/or PDRQ are
asserted HI while the host is resetting CEN and/or PEN, the
request must be acknowledged. The host must assert

CDAK

and/or

PDAK LO and complete a final sample transfer.

Single-Channel DMA

Single-Channel DMA mode allows the AD1845 to be used in
systems with only a single DMA channel. It is enabled by set-
ting the SDC bit in the Interface Configuration Register. All
captures and playbacks take place on the playback channel.
Obviously, the AD1845 cannot perform a simultaneous capture
and playback in Single-Channel DMA mode.

Playback will occur in Single-Channel DMA mode exactly as it
does in Two-Channel mode. Capture, however, is diverted to
the playback channel which means that the capture data request
occurs on the PDRQ pin and the capture data acknowledge
must be received on the

PDAK pin. The CDRQ pin will re-

main inactive LO. Any inputs to

CDAK will be ignored.

Playback and capture are distinguished in Single-Channel DMA
mode by the state of the playback enable (PEN) or capture
enable (CEN) control bits. If both PEN and CEN are set in
Single-Channel DMA mode, playback will be presumed.

To avoid confusion of the origin of a request when switching
between playback and capture in Single-Channel DMA mode,
both CEN and PEN should be disabled and all pending re-
quests serviced before enabling the alternative enable bit.

AD1845

REV. C

Switching between playback and capture in Single-Channel
DMA mode does not require changing the PPIO and CPIO bits
or passing through the Mode Change Enable state except for
initial setup. For setup, assign zeros to both PPIO and CPIO.
This configures both playback and capture for DMA. Following
setup, switching between playback and capture can be effected
entirely by setting and clearing the PEN and CEN control bits,
a technique which avoids having to enter Mode Change Enable.

Dual-Channel DMA

The AD1845 is designed to support full duplex DMA operation
by allowing simultaneous capture and playback. The Dual-
Channel DMA feature enables playback and capture DMA
requests and acknowledges to occur on separate DMA channels.
Capture and playback are enabled and set for DMA transfers.
In addition, Dual-Channel DMA must be set (SDC = 0). It is
not necessary to enter MCE (Mode Change Enable) to change
PEN and CEN (Playback and Capture Enable).

DMA Timing

Below, timing parameters are shown for 8-Bit Mono Sample
Read/Capture and Write/Playback DMA transfers in Figures 22
and 23. The same timing parameters apply to multi-byte trans-
fers. The relationship between timing signals is shown in Fig-
ures 24 and 25.

The Host Interrupt Pin (INT) will go HI after a sample transfer
in which the Current Count Register underflows.

ISA BUS BCLK

DHD1

DBDL

DKSU

DKHDb

CDRQ OUTPUT

CDAK

INPUT

DBEN

& DBDIR

OUTPUTS

INPUT

DATA7:0

OUTPUTS

RDDV

DRHD

STW

Figure 22. 8-Bit Mono DMA Read/Capture Cycle

ISA BUS BCLK

DHD2

STW

DSDL

DKSU

DKHDa

PDRQ OUTPUT

PDAK

INPUT

DBEN

OUTPUT

INPUT

DATA7:0

OUTPUTS

DBDIR OUTPUT

DRHD

WDSU

Figure 23. 8-Bit Mono DMA Write/Playback Cycle

ISA BUS BCLK

CDRQ /PDRQ

OUTPUTS

CDAK

PDAK

INPUTS

DATA7:0

BWDN

LEFT/

LOW BYTE

RIGHT/

HIGH BYTE

Figure 24. 8-Bit Stereo or 16-Bit Mono DMA Cycle

ISA BUS BCLK

CDRQ /PDRQ

OUTPUTS

CDAK

PDAK

INPUTS

DATA7:0

BWDN

LOW

BYTE

HIGH

BYTE

LOW

BYTE

HIGH

BYTE

LEFT

SAMPLE

RIGHT

SAMPLE

Figure 25. 16-Bit Stereo DMA Interrupt

DMA Interrupt

Writing to the internal 16-bit Base Count Register sets up the
count value for the number of samples to be transferred. Note
that the number of bytes transferred for a given count will be a
function of the selected global data format. The internal Cur-
rent Count Register is updated with the current contents of the
Upper and Lower Base Count Registers when a write occurs to
the Upper Base Count Register.

The Current Count Register cannot be read by the host. Read-
ing the Base Count Registers will only read back the initializa-
tion values written to them.

The Current Count Register decrements by one after every
sample transferred. An interrupt event is generated after the
Current Count Register is zero and an additional playback
sample is transferred. The INT bit in the Status Register always
reflects the current internal interrupt state defined above. The
external INT pin will only go active HI if the Interrupt Enable
(wIEN) bit in the Interface Configuration Register is set. If the
IEN bit is zero, the external INT pin will always stay LO, even
though the Status Register's INT bit may be set.

AD1845

REV. C

Hardware Controlled States

The hardware power-down states are accessed by bringing the
PWRDWN or RESET pin LO. Either of these signals place the
AD1845 into the maximum power conservation mode. Bringing
the

PWRDWN or RESET pin HI will power-up the codec in

approximately 512 ms (see the Power-Up and Reset section of
this data sheet).

Power-Down:

PWRDWN immediately puts the AD1845 into

its lowest power-down state. The AD1845's parallel inter-
face will not function and all bidirectional signal lines will be
in a high-impedance state.

Reset:

RESET powers down the AD1845 gradually to its

lowest power-down state. The AD1845 performs a se-
quenced power-down that eliminates audible effects from the
DAC's output. The XTAL1 input must be clocked for the
minimum duration of the

RESET pulsewidth. The

AD1845's parallel interface will not function and all bidirec-
tional signal lines will be in a high-impedance state. Note:
the clock must operate during the software or hardware
power-down process.

Software Controlled States

To enter the Total Power-Down mode requires entering the
Mode Change Enable (MCE) state. After entering MCE, the
Total Power-Down mode can be accessed by writing a "1" to
the TOTPWD bit in the Total Power-Down Register. Exiting
the Total Power-Down mode (writing a "0" to the TOTPWD
bit in the Total Power-Down Register) will initialize the
AD1845 in approximately 512 ms (see the Power-Up and Reset
section of this data sheet).

Total Power-Down: In the Total Power-Down mode the
ADC, DAC, Mixer, and voltage reference are turned off,
but the digital interface remains active awaiting power-up.
All ADC and DAC data is flushed including data in the
capture and playback FIFOs.

To enter the software controlled power-down states in the
Power-Down Control Register, write a "1" to the control bits.

Advanced
Power-Down

PWRDWN

RESET

TOTPWD ADCPWD DACPWD MIXPWD Power-Down

Power-Up

Power

Mode

Pin

Bit

Delay*

Dissipation

Operating

600 mW

1. Power-Down

0 s

512 ms

10 mW

2. Reset

3 ms

512 ms

10 mW

3. Total Power-Down

3 ms

512 ms

150 mW

4. Standby

1/F

180 mW

5. Mixer Power-Down HI

1/F

350 mW

6. Mixer Only

1/F

260 mW

7. ADC Power-Down

1/F

400 mW

8. DAC Power-Down

1/F

425 mW

"x" = Don't Care
*Values shown are derived using a 24.576 MHz input clock source.
All values are proportional to the input clock source.

Figure 26. Advanced Power-Down Mode Summary

POWER-UP AND RESET

The

PWRDWN and RESET pin should be held in the active LO

state when power is first applied to the AD1845. The AD1845's
initialization commences when

PWRDWN and RESET have both

been deasserted (HI). While initializing, the AD1845 ignores all
writes and all reads will yield "1000 0000 (80h)." At the conclu-
sion of initialization, all registers will be set to their default values as
listed in Figure 5. When CDAK and PDAK are inactive during
power-up or reset, the conclusion of the initialization period,
after approximately 512 ms, can be detected by polling the
index register for some value other than "1000 0000 (80h)."

Upon power-up the AD1845 enters the Mode Change Enable
(MCE) state. In the default condition, the AD1845 expects to
receive a 24.576 MHz input clock source. To change the selec-
tion of the current or default input clock source, follow the steps
listed below:

Wait for the AD1845 to initialize.

Set the MODE2 bit to 1.

Enter the MCE state, write to the Crystal/Clock Input Fre-
quency Select bits (XFS2:0) to select the desired frequency.

The AD1845 will now resynchronize its internal states to the
new clock. Writes to the AD1845 will be ignored. Poll the
index register for some value other than "1000 0000 (80h)."

Clear the MCE bit.

ADVANCED POWER-DOWN MODES

The AD1845 has eight Advanced Power-Down Modes available
at any time. The user can control these power-down modes
through hardware by asserting the

PWRDWN and RESET pins

or through software by writing to the Power-Down and the
Total Power-Down Control Registers. Figure 26 summarizes
the power-down delay, power-up delay, and power dissipation
for each power-down mode. A priority listing and description of
the power-down modes follows. Note that the hardware con-
trolled Power-Down and Reset modes take precedence over the
software controlled power-down states.

AD1845

REV. C

The AD1845 performs a sequenced power-down that eliminates
audible effects from the DAC's output, and saves the codec's
internal operating state. Clearing the bits (writing a "0" to the
control bits) returns the AD1845 from the power-down state
and begins the initialization sequence. The AD1845 exits the
power-down mode within 1 sample period. However, an
additional 128 sample periods are required to unmute the out-
puts and restore the internal settings to the pre-Power-Down
operating state.

Standby: Entering the Standby mode places the ADC, DAC
and the Mixer into a low power state, and forces all outputs
to be muted. Standby turns off all internal digital and analog
circuitry with the exception of the digital interface and the
voltage reference. All ADC and DAC data is flushed includ-
ing data in the capture and playback FIFOs.

Mixer Power-Down: Entering the Mixer Power-Down mode,
causes both the mixer and the DAC circuitry to be turned
off. All DAC data is flushed including data in the playback
FIFO. In this mode the mixer is off and the AD1845 is
muted, but the ADC remains functional.

Mixer Only: The Mixer Only mode is initiated by powering
down both the ADC and DAC, leaving the analog mixer and
the digital interface active. MIC, LINE, AUX1, AUX2, and
M_IN can be mixed in the analog domain on the AD1845
outputs. All ADC and DAC data is flushed including data in
the capture and playback FIFOs.

ADC Power-Down: Entering the ADC Power-Down mode,
causes the ADC digital and analog engines to be turned off.
All ADC data is flushed including data in the capture FIFO
and the AD1845 is rendered deaf. The input programmable
gain amplifier (PGA) is also shut down. The DAC and
mixer remain active allowing the AD1845 to continue to
playback and mix samples.

DAC Power-Down: Entering the DAC Power-Down mode
suspends the DAC digital and analog engines, and all DAC
data is flushed including data in the playback FIFO. How-
ever, the mixer and ADC are functional allowing the
AD1845 to continue to capture and mix samples.

AUTOCALIBRATION

The AD1845 calibrates the ADCs and DACs for greater accu-
racy by minimizing dc offsets. Upon power-up or after

RESET,

the AD1845 automatically performs an autocalibration after the
first return from the Mode Change Enable state, regardless of
the state of the ACAL bit. Autocalibration can be forced when
the AD1845 returns from the Mode Change Enable state and
the ACAL bit in the Interface Configuration register has been
set. If the ACAL bit is not set, the RAM normally containing
ADC and DAC offset compensations will be saved, retaining
the offsets of the most recent autocalibration.

The completion of autocalibration can be determined by polling
the Autocalibrate-In-Progress (ACI) bit in the Test and Initial-
ization Register, which will be set during autocalibration. Trans-
fers enabled during autocalibration do not begin until the
completion of autocalibration.

The following summarizes the procedure for autocalibration:

· Set the Mode Change Enable (MCE) bit.

· Set the Autocalibration (ACAL) bit.

· Clear the Mode Change Enable (MCE) bit.

· The Autocalibrate-In-Progress (ACI) bit will remain HI for

384 sample periods. Poll the ACI bit until it transitions from
HI to LO.

· Set desired gain/attenuation/mute and digital mix values.

During the autocalibration sequence, data output from the
ADCs is meaningless. Inputs to the DACs are ignored. Even if
the user specified the muting of all analog outputs, near the end
of the autocalibration sequence, dc analog outputs very close to
V

REF

will be produced at the line output.

CHANGING SAMPLE RATES

In MODE1 the AD1845 can change sample rates by entering
the Mode Change Enable state or writing directly to the Clock
and Data Format Register. In MODE2, the AD1845 changes
sample rates by writing directly to the Upper and Lower Fre-
quency Select Register. Please refer to the following examples
for changing the sample rate.

To change the selection of the current sample rate by entering
the Mode Change Enable state requires the sequence which is
summarized as follows (this is the same sequence used by the
AD1848, AD1846, CS4248, and CS4231):

· Set the Mode Change Enable (MCE) bit.

· In a single write cycle, change the Clock Frequency Divide

Select (CFS2:0) and/or the Clock Source Select (CSS).

· The AD1845 now needs to resynchronize its internal states to

the new clock. Writes to the AD1845 will be ignored. Reads
will produce "1000 0000 (80h)" until the resynchronization is
complete. Poll the Index Register until something other than
this value is returned.

· Clear the Mode Change Enable (MCE) bit.

· If ACAL is set, follow the procedure described in

"Autocalibration" above.

· Wait 128 sample cycles or poll the ACI bit until it transitions

LO.

· Set to desired gain/attenuation values, and unmute DAC

outputs (if muted).

Alternatively, the AD1845 can be programmed to change the
sample rate selection "on the fly" without entering the Mode
Change Enable Sequence. The following sequence applies to
the AD1845 operating in MODE1 or MODE2.

· In a single write cycle, change the Clock Frequency Divide

Select (CFS2:0) and/or the Clock Source Select (CSS). For
compatibility reasons, the AD1845 will send out "1000 0000
(80h)" for approximately 200

s. Even this short wait can be

disabled by setting the INITD bit. When the INITD bit is set,
the AD1845 is ready immediately after changing the sample
rate using CFS and CSS.

· The AD1845 now needs to resynchronize its internal states to

· Set to desired gain/attenuation values, and unmute DAC

outputs (if muted).

AD1845

REV. C

4.3k

1 F

3.3k

560pF

NPO

L_LINE

R_LINE

4.3k

1 F

3.3k

560pF

NPO

Figure 27. 2 V rms Line-Level Input Circuit for LINE Inputs

4.3k

1 F

3.3k

1000pF

NPO

4.3k

1 F

L_AUX1
L_AUX2
M_IN

1000pF

NPO

R_AUX1
R_AUX2

3.3k

Figure 28. 2 V

rms Line-Level Input Circuit for M_IN and

AUX Inputs

The AD1845 codec contains an optional +20 dB gain block to
accommodate condenser microphones. Particular system re-
quirements will depend upon the characteristics of the intended
microphone. Figure 29 illustrates one example of how an elec-
tret condenser mike requiring phantom power could be con-
nected to the AD1845. V

REF

is shown buffered by an op amp; a

transistor like a 2N4124 will also work fine for this purpose.
Note that if a battery-powered microphone is used, the buffer
and R2s are not needed. The values of R1, R2, and C should be
chosen in light of the mic characteristics and intended gain.
Typical values for these might be R1 = 20 k

, R2 = 2 k

, and

C = 220 pF.

L_MIC

REF

1 F

1/2 SSM2135 OR AD820

1/2 SSM2135

OR AD820

R_MIC

LEFT ELECTRET

CONDENSER

MICROPHONE

INPUT

RIGHT ELECTRET

CONDENSER

MICROPHONE

INPUT

0.33 F

1/2 SSM2135

OR AD820

0.33 F

REF

Figure 29. "Phantom-Powered" Microphone Input
Circuit

In the Expanded Mode, MODE2, the AD1845 can be pro-
grammed to change the sample rate selection in 1 Hz incre-
ments "on the fly" and without entering the Mode Change
Enable Sequence. The following sequence applies to the
AD1845 in MODE2 only:

· Enable the Frequency Select Register by setting FREN to 1.

· Change the Lower and Upper Frequency Select Register,

FU7:0 and FL7:0.

APPLICATIONS CIRCUITS

The AD1845 Stereo Codec has been designed to require a
minimum of external circuitry. The recommended circuits are
shown in Figures 27 through 35.

See Figure 1 for an illustration of the connection between the
AD1845 SoundPort Codec and the Industry Standard Archi-
tecture (ISA) computer bus, also known as the "PC-AT bus."
Note that the 74_245 transceiver receives its enable and direc-
tion signals directly from the Codec. Analog Devices recom-
mends using the "slowest" 74_245 adequately fast to meet all
AD1845 and computer bus timing and drive requirements. So
doing will minimize switching transients of the 74_245. This in
turn will minimize the digital feed through effects of the trans-
ceiver when driving the AD1845, which can cause the audio
noise floor to rise. In most applications, the 74_245 can be
omitted and the AD1845 connected directly ISA bus taking
advantage of the AD1845's built-in 16 mA drivers.

Industry-standard compact disc "line-levels" are 2 V rms cen-
tered around analog ground. (For other audio equipment, "line
level" is much more loosely defined.) The AD1845 SoundPort
is a +5 V only powered device. Line level voltage swings for the
AD1845 are defined to be 1 V rms for a sine wave ADC input
and user selectable 0.707 V rms or 1 V rms for a sine wave
DAC output. Thus, 2 V rms input analog signals must be
attenuated and either centered around the reference voltage
intermediate between 0 V and +5 V or ac coupled. The V

REF

pin will be at this intermediate voltage, nominally 2.25 V. It has
limited drive but can be used as a voltage datum to an op amp
input. Note, however, that dc-coupled inputs are not recom-
mended, as they provide no performance benefits with the
AD1845 architecture. Furthermore, dc offset differences be-
tween multiple dc-coupled inputs create the potential for
"clicks" when changing the input mixer selection.

A circuit for 2 V rms mono, line-level inputs and auxiliaries is
shown in Figure 27 and Figure 28. Note that this is a divide-
by-two resistive dividers considering the codec input imped-
ance. The input resistor and 560 pF (1000 pF) capacitor
provides the single-pole of antialias filtering required for the
ADCs. If line-level inputs are already at the 1 V rms levels
expected by the AD1845, the resistors in parallel with the
560 pF (1000 pF) capacitors can be omitted. If the application
does not route the AUX2 inputs to the ADCs, then no antialias
filtering is required (only the 1

F ac coupling capacitor).

AD1845

REV. C

2064pF

XTAL1I

24.576 MHz

XTAL1O

2064pF

Figure 34. Crystal Connections

Note: XTAL2I and XTAL2O, are not used in the AD1845.

Analog Devices also recommends a pull-down resistor for
PWRDWN.

Good, standard engineering practices should be applied for
power-supply decoupling. Decoupling capacitors should be
placed as close as possible to package pins. If a separate analog
power supply is not available, we recommend the circuit shown
in Figure 35 for using a single +5 V supply. Ferrite beads suffice
for the inductors shown (typically 600

at 100 MHz). This

circuitry should be as close to the supply pins as is practical.

0.1 F

10 F

0.1 F

10 F

0.1 F

10 F

0.1 F

+5V

SUPPLY

Figure 35. Recommended Power Supply Bypassing

GROUNDING AND LAYOUT

Analog Devices recommends a split ground plane as shown in
Figure 36. The analog plane and the digital plane are connected
directly under the AD1845. Splitting the ground plane directly
under the SoundPort Codec is optimal because analog pins will
be located above the analog ground plane and digital pins will
be located directly above the digital ground plane for the best
isolation.

Other schemes may also yield satisfactory results. If the split
ground plane recommended here is not possible, the AD1845
should be entirely over the analog ground plane with the op-
tional 74_245 transceiver over the digital plane.

Some manufacturers of compatible devices differentiate between
digital supply pins used to power internal logic and digital sup-
ply pins used to power the ISA bus driver. Their recommended
layout suggests connecting the internal logic supply pins to the
analog supply. A potential problem can occur if the layout con-
nects digital supply pins to the analog supply. Connecting some
of the digital supply pins to one supply and some of the digital
supply pins to a different supply can create an internal short
between the two different +5 V supplies.

Figure 30 shows ac-coupled line outputs. The resistors are used
to center the output signals around analog ground. If dc-cou-
pling is desired, V

REF

could be used with op amps as mentioned

above, if desired.

47k

L_OUT

1 F

R_OUT

1 F

47k

Figure 30. Line Output Connections

A circuit for headphone drive is illustrated in Figure 31. Drive is
supplied by +5 V operational amps. The circuit shown ac
couples the headphones to the line output.

HEADPHONE
LEFT

SSM-2135

10k

470 F

8.66k

10k

HEADPHONE
RIGHT

470 F

L_OUT

V_REF

R_OUT

Figure 31. Headphone Drive Connections

Figure 32 illustrates reference bypassing. V

REF_F

should only be

connected to its bypass capacitors.

REF_F

1.0µF

10µF

REF

Figure 32. Voltage Reference Bypassing

Figure 33 illustrates signal-path filtering capacitors, L_FILT
and R_FILT. The AD1845 must use 1.0

F capacitors; the

AD1845 will not perform properly with 1000 pF capacitors.
The 1.0

F capacitors required by the AD1845 can be of any

type.

1.0µF

L_FILT

1.0µF

R_FILT

Figure 33. External Filter Capacitor Connections

The crystal shown in the crystal connection circuitry of Fig-
ure 34 should be 24.576 MHz, fundamental-mode and parallel-
tuned. Note that using the exact data sheet frequencies is not
required and that external clock sources can be used to over-
drive the AD1845's internal oscillators. (See the description of
the CFS2:0 control bits above.) If using an external clock source,
apply it to the crystal input pins while leaving the crystal output
pins unconnected. Attention should be paid to providing low
jitter external input clocks.

AD1845

REV. C

Analog Devices recommends that all digital pins be driven from
the same supply. A common technique to achieve maximum
performance is to use a +5 V regulator to power the analog side
of the codec from the PCs +12 V supply line, while the standard
PC +5 V supply line powers the entire digital side of the codec.
The separate supplies provide noise isolation for the analog side
of the codec, and maximize performance of the AD1845.

ANALOG

GROUND

PLANE

DIGITAL
GROUND
PLANE

AD1845

PLCC

GNDD

R_AUX2
43

26
R_FILT

ANALOG

GROUND

PLANE

DIGITAL
GROUND
PLANE

AD1845

TQFP

NC
51

25
R_FILT

Figure 36. Recommended Ground Plane

COMPATIBILITY WITH CS4231

1. The CS4231 requires a 1000 pF NPO type capacitor on

Pins 26 and 31. The AD1845 requires a 1

F capacitor on

filter Pins 26 and 31. To achieve compatibility with the
AD1845, use pad spacing that will accommodate either
1000 pF NPO capacitors for the CS4231 and the CS4248
or the 1

F capacitors for the AD1845.

The AD1845 requires the input antialiasing filters for the
ADCs (refer to Figures 27 and 28). The CS4231 can use
the same filters with no degradation in performance. For
compatibility it is suggested that the filters be added.

The CS4231 does not require the power pins (V

) 24,

45, and 54, or the ground pins (GNDD) 25, and 44. It is
suggested that the appropriate power/ground pin connec-
tions be made. This will not affect the performance of the
CS4231.

The CS4231 does not provide software programmable
power-down modes.

The CS4231 does not have the ability to mix the MIC
input with the DAC output.

6. The CS4231 does not contain a Variable Sample Fre-

quency Generator and cannot change sample rates "on the
fly." The CS4231 and CS4248 require entering MCE to
change the sample rate. The AD1845 can change the
sample rate without entering MCE. The AD1845's 50,000
selectable sample rates are not available on the CS4231.
The Variable Sample Frequency Generator reduces clicks
and pops encountered in many game applications.

7. The CS4231 requires two crystal inputs, 24.575 MHz and

16.9344 MHz. The AD1845 requires only one input of
24.576 MHz or can be driven from OSC or other exter-
nal clocks.

8. The CS4231 does not contain the INITD bit.

9. The CS4231 minimum R

= 20 k

. The AD1845 mini-

mum input resistance is 10 k

10. The AD1845 does not include hardware for compressing

and decompressing ADPCM data. Analog Devices offers
Windows based software applets for using ADPCM for-
mats with the AD1845.

AD1845

REV. C

APPENDIX

EXTENDED TEMPERATURE SPECIFICATIONS

Test Conditions
The AD1845 has been tested over the industrial temperature range. The typical values represent the limits that change with tempera-
ture. All other limits remain unchanged.

Temperature

C to +85

DAC Test Conditions

Digital Supply (V

)

5.0 V

Calibrated

Analog Supply (V

)

5.0 V

0 dB Attenuation

Sample Rate (F

)

48 kHz

16-Bit Linear Mode

Input Signal

1008 Hz

Mute Off, OL = 0

Analog Output Passband

20 Hz to 20 kHz

2.0 V

ADC Input Conditions

0.8 V

Calibrated

2.4 V

0 dB Gain

0.4 V

1.0 dB Relative to Full Scale
Line Input
16-Bit Linear Mode

PROGRAMMABLE GAIN AMPLIFIER--ADC

Parameter

Min

Typ

Max

Units

Step Size (All Steps Tested) (0 dB to 22.5 dB)

1.75

PGA Gain Range Span

22.83

AUXILIARY, LINE, MONO, AND MICROPHONE INPUT
ANALOG GAIN/AMPLIFIERS/ATTENUATORS

Parameter

Min

Typ

Max

Units

Step Size AUX1, AUX2, LINE, MIC (All Steps Tested):

(+12 dB to 34.5 dB, Referenced to DAC Full Scale)

1.5

Step Size: M_IN (All Steps Tested) (0 dB to 45 dB)

3.0

Input Gain/Attenuation Range: AUX1, AUX2, LINE, MIC

46.2

Input Gain/Attenuation Range: M_IN

43.5

ANALOG-TO-DIGITAL CONVERTERS

Parameter

Min

Typ

Max

Units

Dynamic Range (60 dB Input THD+N Referenced to

Full Scale, A-Weighted)

THD+N (Referenced to Full Scale)

DIGITAL-TO -ANALOG CONVERTERS

Parameter

Min

Typ

Max

Units

Dynamic Range (60 dB Input THD+N Referenced to

Full Scale, A-Weighted)

THD+N (Referenced to Full Scale)

DAC ATTENUATOR

Parameter

Min

Typ

Max

Units

Step Size (0 dB to 22.5 dB)

1.5

ANALOG OUTPUT

Parameter

Min

Typ

Max

Units

REF

2.36

AD1845

REV. C

Control and Programmed I/O (PIO) Transfers . . . . . . . . . . . 29

DIRECT MEMORY ACCESS (DMA) TRANSFERS . . . . . . . 30

Single-Channel DMA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Dual-Channel DMA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
DMA Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
DMA Interrupt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

POWER-UP AND RESET . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
ADVANCED POWER-DOWN MODES . . . . . . . . . . . . . . . . . 32
AUTOCALIBRATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
CHANGING SAMPLE RATES . . . . . . . . . . . . . . . . . . . . . . . . 33
APPLICATIONS CIRCUITS . . . . . . . . . . . . . . . . . . . . . . . . . 34
GROUNDING AND LAYOUT . . . . . . . . . . . . . . . . . . . . . . . . 35
COMPATIBILITY WITH CS4231 . . . . . . . . . . . . . . . . . . . . . 36
FREQUENCY RESPONSE PLOTS . . . . . . . . . . . . . . . . . . . . 37
APPENDIX--EXTENDED TEMPERATURE

SPECIFICATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

PACKAGE OUTLINE DIMENSIONS . . . . . . . . . . . . . . . . . . 40

FIGURES TABLE OF CONTENTS

1. Interface to ISA Bus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.

-Law or A-Law Expansion . . . . . . . . . . . . . . . . . . . . . . . . 11

-Law or A-Law Compression . . . . . . . . . . . . . . . . . . . . . . 11

4. Direct Register Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
5. Indirect Register Map and Reset/Default States . . . . . . . . . 12
6. Register Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
7. Mix Gain Level Setting: DAC . . . . . . . . . . . . . . . . . . . . . . . 18
8. MODE1 Audio Sample Frequency Select . . . . . . . . . . . . . . 19
9. Digital Audio Data Type . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

10. Mix Gain Level Setting: AUX1, AUX2, MIC, LINE . . . . . 24
11. Mono Attenuation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
12. Capture Audio Data Type . . . . . . . . . . . . . . . . . . . . . . . . . 27
13. Input Frequency Selection . . . . . . . . . . . . . . . . . . . . . . . . . 28
14. 8-Bit Mono Data Stream Sequencing . . . . . . . . . . . . . . . . . 29
15. 8-Bit Stereo Data Stream Sequencing . . . . . . . . . . . . . . . . . 29
16. 16-Bit Mono Data Stream Sequencing, Little Endian . . . . 29
17. 16-Bit Stereo Data Stream Sequencing, Little Endian . . . . 29
18. 16-Bit Mono Data Stream Sequencing, Big Endian . . . . . . 29
19. 16-Bit Stereo Data Stream Sequencing, Big Endian . . . . . . 29
20. Control Register/PIO Read Cycle . . . . . . . . . . . . . . . . . . . . 30
21. Control Register/PIO Write Cycle . . . . . . . . . . . . . . . . . . . 30
22. 8-Bit Mono DMA Read/Capture Cycle . . . . . . . . . . . . . . . 31
23. 8-Bit Mono DMA Write/Playback Cycle . . . . . . . . . . . . . . 31
24. 8-Bit Stereo or 16-Bit Mono DMA Cycle . . . . . . . . . . . . . . 31
25. 16-Bit Stereo DMA Interrupt . . . . . . . . . . . . . . . . . . . . . . . 31
26. Advanced Power-Down Mode Summary . . . . . . . . . . . . . . 32
27. 2 V rms Line-Level Input Circuit for LINE Inputs . . . . . . . 34
28. 2 V rms Line-Level Input Circuit for M_IN and

AUX Inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

29. "Phantom Powered" Microphone Input Circuit . . . . . . . . . 34
30. Line Output Connections . . . . . . . . . . . . . . . . . . . . . . . . . . 35
31. Headphone Drive Connections . . . . . . . . . . . . . . . . . . . . . . 35
32. Voltage Reference Bypassing . . . . . . . . . . . . . . . . . . . . . . . . 35
33. External Filter Capacitor Connections . . . . . . . . . . . . . . . . 35
34. Crystal Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
35. Recommended Power Supply Bypassing . . . . . . . . . . . . . . . 35
36. Recommended Ground Plane . . . . . . . . . . . . . . . . . . . . . . . 36
37. Analog-to-Digital Frequency Response to F

(Full-Scale

Line-Level Inputs, 0 dB) . . . . . . . . . . . . . . . . . . . . . . . . . . 37

38. Analog-to-Digital Frequency Response--Transition Band

(Full-Scale Line-Level Inputs, 0 dB) . . . . . . . . . . . . . . . . . 37

39. Digital-to-Analog Frequency Response to F

(Full-Scale

Inputs, 0 dB) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

40. Digital-to-Analog Frequency Response--Transition Band

(Full-Scale Inputs, 0 dB) . . . . . . . . . . . . . . . . . . . . . . . . . . 37

TABLE OF CONTENTS
PRODUCT OVERVIEW . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Expanded Mode (MODE2) . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

SPECIFICATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
ORDERING GUIDE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
PIN DESIGNATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
PIN FUNCTION DESCRIPTIONS . . . . . . . . . . . . . . . . . . . . . 7
FUNCTIONAL DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . 10

Analog Inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Analog Mixing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Analog-to-Digital Datapath . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Digital-to-Analog Datapath . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Digital Mixing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Analog Outputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Digital Data Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Timer Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Power Supplies and Voltage Reference . . . . . . . . . . . . . . . . . 11
Clocks and Sample Rates . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

CONTROL REGISTERS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Control Register Architecture . . . . . . . . . . . . . . . . . . . . . . . . 11
Direct Control Register Definitions . . . . . . . . . . . . . . . . . . . . 14

Index Address Register (ADR1:0 = 0) . . . . . . . . . . . . . . . . 14
Indexed Data Register (ADR1:0 = 1) . . . . . . . . . . . . . . . . . 14
Status Register (ADR1:0 = 2) . . . . . . . . . . . . . . . . . . . . . . 15
PIO Data Registers (ADR1:0 = 3) . . . . . . . . . . . . . . . . . . . 16

Indirect Control Register Definitions . . . . . . . . . . . . . . . . . . . 16

Left Input Control (IXA3:0 = 0) . . . . . . . . . . . . . . . . . . . . 16
Right Input Control (IXA3:0 = 1) . . . . . . . . . . . . . . . . . . . 16
Left Aux #1 Input Control (IXA3:0 = 2) . . . . . . . . . . . . . . 17
Right Aux #1 Input Control (IXA3:0 = 3) . . . . . . . . . . . . . 17
Left Aux #2 Input Control (IXA3:0 = 4) . . . . . . . . . . . . . . 17
Right Aux #2 Input Control (IXA3:0 = 5) . . . . . . . . . . . . . 17
Left DAC Control (IXA3:0 = 6) . . . . . . . . . . . . . . . . . . . . 18
Right DAC Control (IXA3:0 = 7) . . . . . . . . . . . . . . . . . . . 18
Clock and Data Format (IXA3:0 = 8) . . . . . . . . . . . . . . . . 19
Interface Configuration (IXA3:0 = 9) . . . . . . . . . . . . . . . . . 20
Pin Control (IXA3:0 = 10) . . . . . . . . . . . . . . . . . . . . . . . . . 20
Test and Initialization (IXA3:0 = 11) . . . . . . . . . . . . . . . . . 21
Miscellaneous Control (IXA3:0 = 12) . . . . . . . . . . . . . . . . 21
Digital Mix/Attenuation Control (IXA3:0 = 13) . . . . . . . . 22
DMA Playback Base Count . . . . . . . . . . . . . . . . . . . . . . . . 22

Upper Base Count (IXA3:0 = 14) . . . . . . . . . . . . . . . . . 22

Lower Base Count (IXA3:0 = 15) . . . . . . . . . . . . . . . . . . 23

Alternate Feature Enable /Left MIC Input Control

(IXA3:0 =16) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

MIC Mix Enable/Right MIC Input Control (IXA3:0 = 17) . 23
Left Line Gain, Attenuate, Mute, Mix (IXA3:0 = 18) . . . . 23
Right Line Gain, Attenuate, Mute, Mix (IXA3:0 = 19) . . . 24
Lower Timer Bits (IXA3:0 = 20) . . . . . . . . . . . . . . . . . . . . 24
Upper Timer Bits (IXA3:0 = 21) . . . . . . . . . . . . . . . . . . . . 25
Upper Frequency Select (IXA3:0 = 22) . . . . . . . . . . . . . . . 25
Lower Frequency Select (IXA3:0 = 23) . . . . . . . . . . . . . . . 25
Capture Playback Timer (IXA3:0 = 24) . . . . . . . . . . . . . . . 25
Revision ID (IXA3:0 = 25) . . . . . . . . . . . . . . . . . . . . . . . . . 26
Mono Control (IXA3:0 = 26) . . . . . . . . . . . . . . . . . . . . . . . 26
Power-Down Control (IXA3:0 = 27) . . . . . . . . . . . . . . . . . 27
Capture Data Format Control (IXA3:0 = 28) . . . . . . . . . . 27
Crystal, Clock Select/Total Power-Down (IXA3:0 = 29) . . 27
Capture Upper Base Count (IXA3:0 = 30) . . . . . . . . . . . . 28
Capture Lower Base Count (IXA3:0 = 31) . . . . . . . . . . . . 28

DATA AND CONTROL TRANSFERS . . . . . . . . . . . . . . . . . 29

Data Ordering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
FIFO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Data Bus Drivers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Ð­Ð»ÐµÐºÑ‚Ñ€Ð¾Ð½Ð½Ñ‹Ð¹ ÐºÐ¾Ð¼Ð¿Ð¾Ð½ÐµÐ½Ñ‚: AD1845

ÐÐ»ÐµÐºÑ‚Ñ€Ð¾Ð½Ð½Ñ‹Ð¹ ÐºÐ¾Ð¼Ð¿Ð¾Ð½ÐµÐ½Ñ‚: AD1845