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CHAPTER 4: PERIPHERAL CIRCUITS AND OPERATION (I/O Ports)
4.6.7 Programming notes
(1) When in the input mode, I/O ports are changed from low to high by pull-up resistor, the rise of the
waveform is delayed on account of the time constant of the pull-up resistor and input gate capaci-
tance. Hence, when fetching input ports, set an appropriate wait time.
Particular care needs to be taken of the key scan during key matrix configuration.
Make this waiting time the amount of time or more calculated by the following expression.
10
C
R
C: terminal capacitance 5 pF + parasitic capacitance ? pF
R: pull-up resistance 330 k
(2) When special output (CL, FR) has been selected, a hazard may occur when the signal is turned ON or
OFF.
48
EPSON
S1C63558 TECHNICAL MANUAL
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