HT95LXXX

Rev. 1.20

25

May 26, 2004

Dialer I/O Function

A special dialer I/O circuit is built into the telephone controller for dialing application. These specially designed I/O cells

allows the controller to work under a low voltage condition that usually happens when the subscriber

¢s loop is long.

Dialer I/O pin function:

Name

I/O

Description

XMUTE

NMOS Output

XMUTE pin output is controlled by software. This is an NMOS open drain structure

pulled to VSS during dialing signal transmission. Otherwise, it is an open circuit.

XMUTE is used to mute the speech circuit when transmitting the dialer signal.

DNPO

NMOS Output

DNPO pin is an NMOS output, usually by means of software to make/break the line.

This pin is only controlled by software.

PO

CMOS Output

This pin is controlled by the HKS, HFI and HDI pins.

When PO pin is high, the telephone line is make.

When PO pin is low, the telephone line is break.

HKS

Schmitt Trigger

Input

This pin controls the PO pin directly.

This pin is used to monitor the status of the hook-switch and its combination with

HFI/HDI can control the PO pin output to make or break the line.

A rising edge to HKS pin will cause the dialer I/O to be on-hook status and generate

an interrupt, its vector is 18H.

A falling edge to HKS pin will cause the dialer I/O to be off-hook status and clear HFO

and HDO flags to 0. This falling edge will also generate an interrupt, its vector is 18H.

HDO

CMOS Output

Supported for HT95L400/40P, HT95L300/30P, HT95L200/20P, HT95L100/10P

This pin is controlled directly by HDI, HKS and HFI pin.

When HDO pin is high, the hold-line function is enabled and PO outputs a high signal

to make the line.

HDI

Schmitt Trigger

Input

Supported for HT95L400/40P, HT95L300/30P, HT95L200/20P, HT95L100/10P

A low pulse to HDI pin (hold-line function request) will clear HFO to 0 and toggle HDO

and generates an interrupt, its vector is 18H.

This pin controls the HFO and HDO pins directly.

This pin is functional only when the line is made, that is, off-hook or hand-free

(PO output high signal).

HFO

CMOS Output

This pin is controlled directly by HFI, HDI and HKS pins.

When HFO pin is high, the hand-free function is enabled and PO outputs a high

signal to make the line.

HFI

Schmitt Trigger

Input

A high pulse to HFI pin (hand-free function request) will clear HDO to 0 and toggle

HFO and generates an interrupt, its vector is 18H.

This pin controls the PO, HFO and HDO pins directly.

The following are the recommended circuit for HFI and HDI pins.

0 . 1 m F

H F I P i n

1 0 k W

0 . 1 m F

H D I P i n

1 0 k W

I n t e r n a l P u l l - h i g h 2 0 0 k W

I n t e r n a l P u l l - l o w 2 0 0 k W