Keyboard Information

Pin Description

Pin Name

I/O

Internal

Connection

Description

C1~C4

R1~R4

I/O

CMOS IN/OUT

These pins form a 4

´4 keyboard matrix which can perform keyboard input detec-

tion and dialing specification setting functions. When on-hook (HKS=high) all the

pins are set high. While off-hook the column group (C1~C4) remains low and the

row group (R1~R4) is set high for key input detection.

An inexpensive single contact 4

´4 keyboard can be used as an input device.

Pressing a key connects a single column to a single row, and actuates the system

oscillator that results in a dialing signal output. If more than two keys are pressed at

the same time, no response occurs. The key-in debounce time is 20ms. Refer to

the keyboard information for keyboard arrangement and to the functional descrip-

tion for dialing specification selection.

X1

I

OSCILLATOR

The system oscillator consists of an inverter, a bias resistor and the necessary

load capacitor on chip. Connecting a standard 3.579545MHz crystal or ceramic

resonator to the X1 and X2 terminals can implement the oscillator function. The

oscillator is turned off in the standby mode, and is actuated whenever a key-

board entry is detected.

X2

O

XMUTE

O

NMOS OUT

XMUTE is an NMOS open drain structure pulled to VSS during dialing signal

transmission. Otherwise, it is an open circuit. The XMUTE is used to mute the

speech circuit when transmitting the dial signal.

HKS

I

CMOS IN

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.

HKS=VDD: On-hook state (PO=low). Except for HFI/HDI

(hand-free/hold-line control input), other functions are all disabled.

HKS=VSS: Off-hook state (PO=high). The chip is in the standby mode and

ready to receive the key input.

PO

O

CMOS OUT

This pin is a CMOS output structure, which by receiving HKS and HFO/HDO

signals, control the dialer to connect or disconnect the telephone line.

PO outputs a low to break the line when HKS is high (on-hook) and HFO/HDO

is low. PO outputs a high to make the line when HKS is low (off-hook) or HFO is

high or HDO is high.

During the off-hook state, the pin also outputs the dialing pulse train in pulse

mode dialing. While in the tone mode, this pin is always high.

MODE

I/O

CMOS IN/OUT

This is a three-state input/output pin, used for dialing mode selection whether

Tone mode or Pulse mode; 10pps/20pps.

MODE=VDD: Pulse mode, 10pps

MODE=OPEN: Pulse mode, 20pps

MODE=VSS: Tone mode

During pulse mode dialing, switching this pin to the tone mode changes the

subsequent digit entry to tone mode. When the chips are in tone mode, switch-

ing to the pulse mode will also be recognized.

HT9302 Series

Rev. 1.20

3

September 30, 2002

H T 9 3 0 2 A / B / C / D

1

4

7

* / T

2

5

8

0

3

6

9

#

S A

.

P

R

R 4

R 3

R 2

R 1

C 4

C 1

C 2

C 3

H K S

H T 9 3 0 2 G

1

4

7

* / T

2

5

8

0

3

6

9

#

.

P

R

R 4

R 3

R 2

R 1

C 1

C 2

C 3