Canon A-200 series Service Manual page 137

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Keyboard failure
* XX 301
XX is the key code whose key switch is always on, refer to Table 6-11 and replace it.
* 301
Key Reset is not completed.
Check the PPI (CS, AO, A1,
RO,
WR, and 00-07 signals).
Check the interface signals.
97.5-260/.15
KCLK
Start Bit
P10
P21---::...-----~
P22--~----~~---~
15t data 2nd data
Figure 8-2
134