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
