Data Sheet

AS2574B

Rev. 1

2

Jan. 1995

Pin #

Pin Node

Description

1

OSC2

Oscillator pins for ceramic resonator (681 kHz)

2

OSC1

3

SCL

The SCL output is used to clock all data into the display driver

4

SDA

The SDA output is used to transfer data into the display driver

5 - 10

C1 - 6

Keyboard columns

11 - 15

R1 - 5

Keyboard rows

16

LS

Output for controlling loudhearing and handsfree facilities, active high

(see hook state diagramme)

17

MASK

Mask output, active high during pulsing (make and break period, see timing

diagrammes).

18

CD

Chip disable input, active low.

When CD is low, the circiut is disabled.

If this pin is pulled to V

2 sec., the circuit is reset*. If the pin is pulled to V

line break is ignored.

* If in ACP or monitor state, reset also means return to idle state.

19

MR

Mute output, active high during signalling (see timing diagrammes).

20

MT

Transmit mute output, active high when MR is high and when

the Mute key has been activated (see timing diagrammes).

21

ER

Earth recall input/output, active high during ER but when forced to V

the flash is enabled.

22

DT

Dial tone input.

This input is scanned when invoking ACP or a pause is read in a digit string:

DT pin

Function

Open

Pause duration 4.1 sec

Low

If a high is not detected within 8 sec., the circuit is

reset *

High

If the pin is high for > 1.15 sec., the pause is termi-

nated and the dialling continued. Noise immunity > 8 ms

* Reset means that dialling is stopped and the circuit returns to standby.

If the circuit was in ACP state, the reset will also return the circuit to idle state.

23

DP

Hook switch control, dial pulse and flash output; low during Idle and break

periods and high during off-hook (see timing diagrammes).

PinDescription

Continues…