Keyboard Information

Block Diagram

Pin Description

Pin Name

I/O

Internal

Connection

Description

C1~C4

R1~R4

I/O

CMOS

IN/OUT

These pins form a 4

keyboard input detection and dialing specification setting

functions. When the chip is in the standby mode the column

group (C1~C4) remains low whereas the row group (R1~R4) is

set high for key input detection.

An inexpensive single contact 4

input device. Pressing a key connects a single column to a

single row, and actuates the system oscillator which result in

a dialing signal output. If more than two keys are pressed at a

time, no response occurs. The key-in debounce time is 20ms.

Refer to the keyboard information for keyboard arrangement.

HT9201A/B

2

3rd Dec ’97