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6. BLOCK DIAGRAM
7. CIRCUIT OPERATIONS
7.1. KEY INPUT CONTROL CIRCUIT
1) Circuit Operation
Sequential input information (negative logic) from the DSHS proprietary telephone is executed
by dynamic scanning.
The ports RR70 to RR73, RR80 to RR83 of IC6 are brought to low status consecutively.
If a key is pressed, the key-in information input is executed by ports R91 to R93, RB1, RB11,
RB21, RB0, RD1.
7.2. LCD CONTROL CIRCUIT
17
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