Data Sheet

Rev. 3

AS2578 /B

March 1997

TELEPHONE CONTROLLER WITH

13 MEMORIES AND 2-WIRE BUS

Key Features

Low operating voltage

Low current consumption, standby

0.1

Oscillator using Xtal or ceramic resonator (3.58 MHz)

Serial interface to external EEPROM

Consistent, simple and usable procedures

The settings are programmed via the keyboard and
stored in EEPROM or set by pin options
Dialler:

Data protection with 20 digit FIFO

Sliding cursor protocol with comparison

Automatic pause generation

Temporary MF select via keyboard

30 digit LNR (Last Number Redial)

13 x 20 digit memory (RAM) on chip
Tone Ringer:

Ring frequency discrimination

3 tone melody with 4 different repetition rates

Volume of melodies can be set in 4 steps

Block Diagramme

General Description

The AS2578 /B are a versatile repertory LD/MF diallers
with a melody generator, a ring frequency discriminator
and a 2-wire interface to EEPROM. Together with the
AS2520/1, the AS2578 /B form a coherent basis for a
fully electronic telephone with a wide range of options.

The AS2578 /B are especially designed to adapt to
different PTT specifications. A RAM is on chip for last
number redial, 3 direct dial and 10 numbers with
abbreviated dialling. To allow easy use under a PABX,
the device incorporates automatic pause insertion and
sliding cursor procedure as selectable options (AS2578)
or centrex keys (AS2578B). The device can be used with
or without EEPROM as appropriate. When an EEPROM
is connected, all RAM content is stored in the EEPROM
by power loss.

The circuit provides the possibility to set different modes
of operation (LM codes) via the keyboard or via pin
options, e.g. default signalling mode, automatic pause
insertion, flash or ground loop and settings of volume
and melodies.

Austria Mikro Systeme International

KEYSCAN

HOOK

STATE

CONTROL

DIAL

DTMF

MELODY

SERIAL

INTERFACE

RING

FREQUENCY

DETECTOR

POR

OSCILLATOR

REDIAL

13 X 20

1 X 30

RAM
FIFO

MUTE

SET

LNR

3.58 MHz

MUTE

SCL

SDA

FCI

MASK

MODE

AP (AS2578 only)

AS2578 /B

Vss V

MEM

(AS2578B)

Package

Available in 28 pin DIP and PLCC.

Data Sheet

Rev. 3

AS2578 /B

March 1997

Pin Description

Pin #

Symbol

Function

Keyboard Columns

Hook Switch Input
This input is active high with internal pull-down resistor.

MODE

Signalling (LD/MF) Default Mode Select Input

Mode pin

Function

High

LD default mode, make/break pulse 33/66 ms

Open

MF only

Low

LD default mode, make/break pulse 40/60 ms

Chip Enable Input
This input is active high with internal pull-down resistor and is used to initiate setup
procedures.

OSC2

Oscillator Input

OSC1

Oscillator Output
Oscillator pins for Xtal or ceramic resonator (3.58 MHz). When a ceramic resonator is used
a capacitor (10 - 22 pF) must be connected from each of the oscillator pins to V

Vss

Negative Power Supply

TONE

DTMF Tone Output
The dual tones provided at this output have a level independent of the supply voltage in
the operating range from 2.5 to 5.5V.

SDA

Serial Data I/O
SDA is a bidirectional pin with an open drain with internal pull-up resistor and is used to
transfer data into and out of a compatible EEPROM.

SCL

Serial Clock Line Output
The SCL output is an open drain with internal pull-up resistor and is used to clock data into
and out of a compatible EEPROM.

FCI

Frequency Comparator Input
Schmitt trigger input for ring frequency discrimination.

Melody Generator Output
Melodies for tone ringing are generated on this output. The output signal is PDM.

MUTE

Mute Output
This push-pull output is high during dialling and when mute key has been activated,
otherwise low.

MASK

Mask Output
This push-pull output is high during pulsing (make and break periods).

Continues...

Data Sheet

Rev. 3

AS2578 /B

March 1997

Pin Description cont´d

Pin #

Symbol

Function

DPN

Dial Pulse Output
This is the push-pull output for controlling the hook-switch transistor. It is low during on-
hook and break periods and high during off-hook (see timing diagrammes).

Ground Loop Output
This push-pull output is high during ground loop

Positive Power Supply

Keyboard Rows

Keyboard Column (AS2578)
This column is for the memory keys

Keyboard Column (AS2578B)
This column is for centrex keys (A - D keys). Automatic pause insertion and Temporary
MF select 1 are fixed enabled (AP open)

Access Pause Select Input (AS2578)
This input is used to select the automatic access pause insertion or sliding cursor (no
centrex keys):

AP pin

Function

High

Sliding cursor enabled

Temporary MF select 2

Open

Automatic pause insertion enabled

Temporary MF select 1

Low

Sliding cursor and pause disabled

Temporary MF select 1

Keyboard Column (AS2578B)
This column is for the memory keys

Melody Volume Select Input
This input is used to select the volume of the melodies in 4 steps by connecting the MV
pin to row 1, 2, or 3. Leaving the pin open is the default setting (max. volume).

Repetition Rate Select Input
This input is used to select the repetition rate of the melodies. 4 different rates can be
selected by either leaving the pin open (default) or connecting it to column 1, 2, or 3.

Power On Reset

The on chip power on reset circuit monitors the supply
voltage (V

). As long as V

remains below the internal

reference voltage, Vref (typically 1.1V), the oscillator is
inhibited. When V

rises above Vref (t

RISE

= 1

s/V to 50

ms/V), a reset signal is generated to assure correct start-
up.

Initial Setup

A low to high transition on the CE input will initiate an
automatic setup, i.e. the pin options are scanned and
(when an EEPROM is connected) the stored LM codes
and melody settings are read from the EEPROM. This is
done independently of the hook state (see timing
diagrammes).

Note: "Open" means

100 k

Data Sheet

Rev. 3

AS2578 /B

March 1997

Memory Keys

The keys M1 to M3 are direct memory access keys and
the MEM key is used for abbreviated dialling.

13 numbers can be stored in on chip RAM. Each number
can contain up to 20 digits (including pauses).

If an EEPROM is connected to the serial bus, the content
of the RAM is written into the EEPROM when CE is
turned low indicating a power loss.

During programming multible pauses can be inserted by
pressing the LNR key.

Memory dialling is cascadable.

Mode Selection

The default mode (LD or MF) can be selected by the
MODE pin.

Furthermore, the mode can be selected by setting the
LM code (see setup menu). If no LM code is set, the
mode will be determined by the MODE pin.

When default LD mode is selected, a temporary change
to MF mode can be invoked by pressing * (AP = high,
AS2578 only) or Set, * , Set.

When the circuit is in temporary MF mode, each of the
following procedures revert it to default LD mode:

- pressing Set, * , Set ,

- pressing recall key (by further entries of the recall key

the signalling mode will toggle between MF and LD,

- by next On-hook.

Recall Function

A recall activation will invoke a flash (timed loop break)
or a ground loop (GL) depending on the selected LM
code, which is stored in the external EEPROM (see
setup menu).
If no LM code is set, depressing the recall key will invoke
both a flash and a GL, however, in LD mode a Flash is
never executed.

If recall is the first entry in a digit string, it will be stored

in LNR RAM when digit(s) are entered after the recall.

If the recall key is depressed after a digit string has been
entered or dialled out, the recall will not be stored, and
subsequently entered digits will be stored in the LNR
RAM as the new number.

If pressing the recall key is not followed by digit entries,
the LNR RAM remains intact.

Last Number Redial

LNR is a facility that allows resignalling of the last
manually dialled number without keying in all the digits
again. The LNR is repeatable.

The current contents of the RAM are overwritten by new
entries.

A manually entered number is automatically stored in the
LNR RAM. The capacity of the RAM is 30 digits. If a
number greater than 30 digits is entered, the LNR facility
will be inhibited (until new entries < 31 digits) and further
entries will be buffered in FIFO.

Postdialled digits, i.e. digits manually entered after LNR
has been invoked, are not stored in RAM but buffered in
FIFO.

Valid Keys

The keyscanning is enabled when CE or HS are high.
During setup the keyboard is disabled. A valid key is
detected from the keyboard by connecting the appropriate
row to the column. This can be done using an n x m
keyboard matrix with single contacts. Positive and
negative edges of each contact are debounced. The
debounce time is 15 ms.

Mute Key

The mute key is only enabled when off-hook. Depressing
the mute key activates and deactivates (toggle switch)
the MUTE output, when internal mute is inactive, i.e. in
speech mode.

Any key entry overwrites a mute activated by the mute
key, and mute will be deactivated.

Centrex Keys (AS2578B only)

The alphameric keys accommodate easy use of centrex
services. The A, B, C and D keys are only valid in MF
mode and are not storable. Pressing one of these keys
will invoke the appropriate MF tones to be transmitted.
The centrex keys are not stored in the RAM, but are
buffered in the FIFO, and subsequently entered digits
are also buffered in the FIFO.

Pressing the recall key after a sequence including centrex
keys will reset the RAM counter, and subsequently
entered digits will be stored in the RAM. If MF select (Set,
* , Set) has been invoked once, then all susequently
digits/data will be buffered in the FIFO.

Data Sheet

Rev. 3

AS2578 /B

March 1997

After a recall a pause will automatically be generated.
The pause time is 3 sec.

The ground loop (GL) has two pulse lengths, namely a
short of 500 ms and a long of 1250 ms.

Short GL: If the recall key is depressed for

540 ms, the

GL pulse is 500 ms.

Long GL: If the recall key is depressed for > 540 ms, the
GL pulse is 1250 ms.

During redial a ground loop is only executed as a long GL
(1250 ms).

Pause Generation

Pause introduces a delay in signalling digit strings to
accommodate second and subsequent dial tones.

Automatic pauses are generated in the following manner:

- always after a recall independent of the AP pin

- with automatic pause insertion enabled by pin option

or LM code, up to two pauses can be automatically
inserted at any location of the original entry in the RAM
(except location 1 of the digit string), when the mute
output goes inactive (in MF mode for more than 1 sec.)
before next entry.

A pause read from the RAM can be terminated (shortened)
prior to time out by a low level on AP pin (AS2578 only)
during the pause execution. The pause time is 3 sec.

During execution of a pause, mute is inactive, i.e. the
circuit is in speech mode.

Sliding Cursor Procedure (AS2578 only)

To accommodate redialling (LNR) behind a PABX without
using automatic pause generation, a sliding cursor
protocol is implemented. The sliding cursor is enabled
when AP = high. If new entries match the previous RAM
contents, pressing the LNR key will dial out the remaining
digits.

If there is an error in matching, the LNR will be inhibited
until next on-hook, and the RAM will contain the new
number.

Serial Interface

The AS2578 /B support a bidirectional bus oriented

protocol. The protocol defines any device that sends
data onto the bus as a transmitter, and the receiving
device as the receiver. The AS2578 /B are controlling the
transfer and hence the master. The EEPROM being
controlled is the slave.

The AS2578 /B will always initiate data transfer, and
provide the clock for both transmit and receive operations.
Therefore, the protocol is for single master applications
only.

However, a temporary second master can be used to
write into the EEPROM when the AS2578 /B are supplied
and in idle state.

Clock and Data Conventions
Data states on the SDA line can change only during SCL
low. SDA state changes during SCL high are reserved
for indicating start and stop conditions (see figure 1 and
2).

Start Condition
All commands are preceded by the start condition, which
is a high to low transition of SDA when SCL is high. The
slave should continuously monitor the SDA and SCL
lines for the start condition and must not respond to any
command until this condition has been met.

Stop Condition
All communications are terminated by a stop condition,
which is low to high transition of SDA when SCL is high.
The stop condition is also used to place the slave in the
standby power mode.

Acknowledge
Acknowledge is a software convention used to indicate
successful data transfers. The transmitting device, either
master or slave, will release the bus after transmitting
eight bits. During the ninth clock cycle the receiver will
pull the SDA line low to acknowledge that it received the
eight bits of data (see figure 3).

The slave should always respond with an acknowledge
after recognition of a start condition and its slave address.
If both the device and a write operation have been
selected, the slave should respond with an acknowledge
after receipt of each subsequent eight bit word.

In the read mode, when the EEPROM has transmitted
eight bits of data, it should release the SDA line and
monitor the line for an acknowledge. If the AS2578 /B
respond with an acknowledge and does not generate a
stop condition, the EEPROM should continue to transmit
data. If the AS2578 /B do not respond with an
acknowledge, the EEPROM should terminate further

Data Sheet

Rev. 3

AS2578 /B

March 1997

data transmission and await the stop condition to return
to the standby power mode.

data

change

data

stable

SDA

SCL

Figure 1 Data Validity

start

bit

stop

bit

SDA

SCL

Figure 2 Definition of Start and Stop

SCL from
master

Data out
from Tx

Data out
from Rx

start

acknowledge

Figure 3 Acknowledge Response From Receiver

Frequency Comparator

The frequency comparator monitors that the ring signal
is in the limits as shown in figure 4.

Tone Generator

The tone generator incorporates the DTMF tones and 3
basic frequencies for the tone ringer.

DTMF
The DTMF generator provides 8 frequencies, namely:

Low group

Row 1

697 Hz

Row 2

770 Hz

Row 3

852 Hz

Row 4

941 Hz

High group

Col. 1

1209 Hz

Col. 2

1336 Hz

Col. 3

1477 Hz

Col. 6

1633 Hz

(AS2578B only)

The MF tones are in accordance with CEPT
recommendations.

Tone Ringer (Melody)
The three basic frequencies of the melodies are:

F1 = 800 Hz, F2 = 1067 Hz, and F3 = 1333 Hz (

5%).

The repetition rate can be set via key procedures or by
pin options as follows:

LM code

Repetition rate

1 time

(50 ms pause)

2 (default)

4 times

7 times

10 times

Repetition rate means that a sequence of 6 frequencies
is repeated 1 to 10 times within 1 sec. For LM code 1 a
pause of 50 ms is inserted between the frequencies to
allow a better recognition of the melodies.

The sequence of the frequencies is controlled by the
sequence register as follows:

Sequence

F1 F2 F3 F1 F2 F3 ...

The volume of the melodies (MO output) can be set as
follows:

LM code

Volume

Steps

- 17.5 dB

- 11.5 dB

6 dB

- 5.5 dB

6 dB

(default)

0 dB

5.5 dB

When a continious valid ring signal is present for 80 ms,
the melody generator is activated and remains active
until two or more periods of the ring signal are missing.

Ring

frequency

(Hz)

MUST

DETECT

Tol.

Figure 4 Detection Window of Ringing Signal

Data Sheet

Rev. 3

AS2578 /B

March 1997

LM Codes and Pin Options

LM code

Pin option

Function

02-2*

AP = L

Automatic pause insertion: off

Sliding cursor: off

MF select 1

02-3

AP = Hi-Z

Automatic pause insertion: on

Sliding cursor: off

MF select 1

AP = H

Automatic pause insertion: off

Sliding cursor: on

MF select 2

033*

MODE = L

LD mode 40/60

033*

MODE = H

LD mode 33/66

036

MF mode

037

MF mode

Flash

MODE = Hi-Z

MF mode

GL + Flash

250

Resets all user settings to default and clears all RAM contents

258

Clears all RAM contents

5 - 4*

MV = Hi-Z

Melody volume:

0 dB

5 - 3

MV = R3

Melody volume:

- 5.5 dB

5 - 2

MV = R2

Melody volume:

- 11.5 dB

5 -1

MV = R1

Melody volume:

- 17.5 dB

6 - 1

RR = Hi-Z

Repetition rate:

1 time

(50 ms pause)

6 - 2*

RR = C1

Repetition rate:

4 times

6 - 3

RR = C2

Repetition rate:

7 times

6 - 4

RR = C3

Repetition rate:

10 times

Note 1: Programming an LM code overwrites pin options, however, LM code 033 can only be selected when the MODE

pin is connected to either high or low for selecting the make/break ratio. Not valid LM codes are ignored. LM
codes with a '*' are default settings.

Note 2: When the AP pin is pulled low during execution of a pause, the pause will be terminated.

Note 3: AP pin option not available on AS2578B.

Data Sheet

Rev. 3

AS2578 /B

March 1997

Operating Procedures

Procedure Principles
The procedures for utilizing the features of the AS2578 /B are optimized out of consideration for the human factor in
order to:
- meet the user´s expectations
- be easy to learn and relearn
- not invoke any automatic functions which the user doesn´t expect
- protect the user from committing critical errors, e.g. dialling wrong numbers, etc.
- be consistent, simple and usable
- meet the German 1 TR 2 and ETR 2 specifications.

Idle (on-hook,
no ringing)

Speech mode

Programming

False programme
entry

Invalid entry

TEXT

State according
to text

Privacy mute

Ringing

KEY

Going off-hook

Going on-hook

Pressing a key

Entering a
number

Entry according
to text

TEXT

1590

Enter
password

sec

Time out (x sec.)

Dialling
(LD or MF)

Storing (writing into
RAM or EEPROM)

Processing
according to text

TEXT

Melodies activated
(ringing)

= reading from
memory

States:

Entries:

Processing:

Symbols

Data Sheet

Rev. 3

AS2578 /B

March 1997

Setup Procedures

SET

5 or 6

Temporary MF Select

Programming Melody

ANY OTHER

ENTRY

sec

SET

Exit programme state

1590

LNR

Clear

Procedures

FALSE

LNR

ANY OTHER

ENTRY

LM Codes

022 or 023 or

033 or 036 or 037

LM Code

250

LNR

SET

022, 023 executed.

033, 036, 037

buffered

LNR

SET

LM Code

258

LNR

SET

ANY OTHER

SEQUENCE

LNR

LM Codes:

022 = no AP, no SC
023 = AP, no SC

033 = LD (MODE pin = V

or Vss), GL

036 = MF, GL
037 = MF, FL

250 = Resets all settings to default, inhibits LNR

and memories

258 = Inhibits LNR and memories

Resets all

settings

to default

022, 023 executed.

033, 036, 037

buffered

M1-3

MEM

Storing Direct Numbers

Storing Indirect Numbers

Data Sheet

Rev. 3

AS2578 /B

March 1997

Electrical Characteristics

Absolute Maximum Ratings

Positive Supply Voltage ...................................................................................................................-0.3V

Input Current ................................................................................................................................................

25 mA

Digital Input Voltage ......................................................................................................V

- 0.3V

+ 0.3V

Electrostatic Discharge (HBM) ........................................................................................................................

800V

Storage Temperature ......................................................................................................................-65

C to +125

Recommended Operating Conditions

Supply Voltage (except DTMF) .....................................................................................................2.2V

5.5V

Supply Voltage (DTMF) .................................................................................................................2.5V

5.5V

Oscillator Frequency ..................................................................................................................................3.58 MHz

Operating Temperature ....................................................................................................................- 25

C to +70

DC Characteristics (Default conditions: recommended operating conditions; outputs unloaded; V

= 3.5V;

AP and MODE = Vss; unless otherwise specified))

Symbol

Parameter

Conditions

Min

Typ

Max

Units

DD0

Standby Current

HS = L; CE = L

0.1

Standby Current

HS = H; Osc. = 0

3.6

Operating Current

no tones

400

700

Operating Current

MF/melody

0.9

1.5

Input Voltage, Low

0.2 V

Line Voltage, High

0.8 V

Output Current, Sink

= 0.4V

1.5

Output Current, Source

= V

- 0.4V

Pull-down Resistor

AC Charateristics (Default conditions: recommended operating conditions)

Symbol

Parameter

Conditions

Min

Typ

Max

Units

Clock Startup Time

Key Debounce Time

14.7

HS Debounce Time

14.7

Setup Time

100

Continues...

Data Sheet

Rev. 3

AS2578 /B

March 1997

AC Characteristics Cont´d

Symbol

Parameter

Conditions

Min

Typ

Max

Units

DTMF

MF Tone Level

High group, R

= 15 k

-12.3

-10.8

-9.3

dBm

L-H

Preemphasis Low to High

= 15 k

2.0

2.4

2.8

THD

Distortion (0.3 - 4 kHz)

= 15 k

, note 3

-23

dBr

Tone Duration

Note 1

82.3

ITP

Inter Tone Pause

Note 1

82.3

Tone Rise Time

Note 2

Tone Fall Time

Note 2

Dial Rate

pps

M/B

Make/Break Period

5%, MODE = low

40.8/61.2

5%, MODE = high

33/66

IDP

Inter Digit Pause

800

840

880

Mute Overhang

Flash Duration

100

102

GLS

Ground Loop, Short

R key

540 ms

495

500

505

GLL

Ground Loop, Long

R key > 540 ms

1200

1250

1300

Automatic Pause

2.9

3.0

3.1

sec

Melody

Melody Output

PDM

Melody Delay

Frequency 1

770

800

830

Frequency 2

1025

1067

1110

Frequency 3

1280

1333

1385

Detection Time

Detection Time-out

note 4

MIN

Min. Detection Frequency

MAX

Max. Detection Frequency

Note 1: The values are valid during automatic dialling and are minimum values during manual dialling, i.e. the tones will

continue as long as the key is depressed.

Note 2: The rise time is the time from 10% of final value till the tone amplitude has reached 90 % of its final value.
Note 3: Relative to high group.
Note 4: The FCI circuit is reset by POR and on-hook. After a reset the FCI circuit is in a standby state. A positive edge on FCI

will start the 73 ms timer and the frequency discrimination is initiated. Whenever a period of the ring frequency is
missing, the timer is reset. When a valid ring signal is present for

73 ms, the melody generator is started and is

directly controlled by a valid signal from the FCI circuit. This condition will remain until a new reset.

Data Sheet

Rev. 3

AS2578 /B

March 1997

Pin Configurations

AS2578

TONE

MASK

MUTE

MODE

Vss

OSC2

OSC1

SDA

SCL

FCI

AS2578B

TONE

MASK

MUTE

MODE

Vss

OSC2

OSC1

SDA

SCL

FCI

MODE

Vss

OSC2

OSC1

TONE

SCL

FCI

MUTE

MASK

SDA

AS2578B

28 Pin PLCC

28 Pin DIP

MODE

Vss

OSC2

OSC1

TONE

SCL

FCI

MUTE

MASK

SDA

AS2578

Data Sheet

Rev. 3

AS2578 /B

March 1997

Ordering Information:

Part Number

Package

Pin 25

Pin 26

AS2578 P

28 pin DIP

AS2578 N

28 pin PLCC

AS2578B P

28 pin DIP

AS2578B N

28 pin PLCC

Applications:

For application support contact your local AMS sales office.

1995-7, Austria Mikro Systeme International AG, Schloss Premstätten, 8141 Unterpremstätten, Austria. Trademarks

Registered

the prior written consent of the copyright owner.

Devices sold by Austria Mikro Systeme are covered by the warranty and patent indemnification provisions appearing in its Term of
Sale. Austria Mikro Systeme makes no warranty, express, statutory, implied, or by description regarding the information set forth
herein or regarding the freedom of the described devices from patent infringement. Austria Mikro Systeme reserves the right to
change specifications and prices at any time and without notice. Therefore, prior to designing this product into a system, it is necessary
to check with Austria Mikro Systeme for current information. This product is intended for use in normal commercial applications.
Applications requiring extended temperature range, unusual environmental requirements, or high reliability applications, such as
military, medical life-support or life-sustaining equipment are specifically

not recommended without additional processing by Austria

Mikro Systeme for each application.

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