OKIDATA OKIOFFICE 44, Service Manual

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Board Descriptions A - 42 OKIOFFICE 44 Serv. Man., P/N 59276801
A3.3 OPE (04W) Circuit Diagram
1. Block diagram
Figure A3.3.1 shows a block diagram of OPE (04W).
The 04W (operation unit) circuit consists of the following blocks:
1) IC1 (one chip MOS-CPU)
• Output ports
Setting LEDs on and off: 8 ports
Specifies the row during key switch matrix scanning: 8 ports
• Input ports
Detect the column whose key is pressed: 8 ports
2) Key switch matrix (8 rows x 8 columns)
3) LEDs (8 LEDs)
4) LCD unit
2. Key switch scanning
Output ports (KSCAN0 to KSCAN7 signal) corresponding to 8 rows of key matrix are scanned
sequentially by the software. In the case 1 is any of output from KSCAN0 to KSCAN7 signal
which corresponds to the row 8 in the block diagram, the software reads input port, KSENS0 to
KSENS7, and determines which in the row 8 is pressed.
3. LED drives and LEDs
Eight LEDs (ALARM, PHOTO, LIGHT, etc.) on the control panel are driven by output of IC1 via
resistors R1, R4-9 and R11 respectively. An LED lights on when a port output is 1.