11-6 403 – 447 MHz UHF1 Theory Of Operation: Keypad
11.5 Keypad
Left, Right and P1 to P3 keys are directly connected to microprocessor via 22 Pin connector. When
any of these keys is pressed, the voltage goes “low” and microprocessor detects it.
For full keypad models, the number keys are in matrix type which consisted of 3 rows and 4 columns.
When any of these keys is pressed, the voltage goes “low” and microprocessor interprets the voltage
for each key press.
Figure 11-4. Keypad Block Diagram
KEYPAD
Left
NUMBERS
Right
P1 P2 P3
Key
Key row
Key
column
22pin connector
Keypad board
22pin connector
Main board
MCP
detect
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