8-1
Section 8
KEYPAD BOARD INFORMATION
1.0 Theory of Operation
Keypad
U602 is a comparator that will compare the voltage when any one of the keypad row or keypad
column keys is being pressed. Therefore when a key is being pressed, it will send a message to the
microprocessor through the output (KEY_INT) telling it that a key has been pressed. The
microprocessor will then sample the Analog to Digital voltages at the keypad row and keypad
column and map it with the table so that the key being pressed can be identified.
2.0 Troubleshooting Chart
Figure 8-2 Keypad Board Troubleshooting Chart
Figure 8-1 Keypad Block Diagram
40 pin connector
Comparator
Keypad
Button
9 pin connector
Key_Int
Keypad Column
Keypad
Data
Row
Tone
End
Disconnect and
reconnect 40-pin
flex
No
Yes
Press Keypad
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