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Hardware Overview Theory of Operation

1 - 10 0070-10-0591-01 Trio™ Service Manual

1.2.5 Keypad Board

P/N 0671-00-0058

FIGURE 1-7 Keypad block diagram

1.2.5.1 Detailed Description

This module detects key and encoder input signals, converts them into code then sends these

coded signals to the main board. The main control board (Host CPU board) in turn sends

commands back to the keyboard's control indicator and audio process circuits, which enable

or disable audio and visual alarm respectively, as required.

CPU

• Detects key and encoder input signals;

• Controls LED status;

• Controls Audio Process Circuit;

• Regularly zeroes Watchdog Timer;

• Communicates with main board.

Audio Process Circuit

Generates audio signals to drive the speaker.

Watchdog

• Upon power-up, supplies Reset signal to CPU;

• Provide functions of Watchdog Timer Output and voltage detection.

Watchdog

ENCODER

KEY

CPU

(AT89C51)

RAM

128 X 8

FLASH

4K X 8

Main Control

board (Host CPU Board)

Audio Process

Circuit

SPEAKER

LED

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