Programming Notes - Epson S1C63558 Technical Manual

CHAPTER 4: PERIPHERAL CIRCUITS AND OPERATION (Input Ports)

4.4.5 Programming notes

(1) When input ports are changed from low to high by pull-up resistors, the rise of the waveform is
delayed on account of the time constant of the pull-up resistor and input gate capacitance. Hence,
when fetching input ports, set an appropriate waiting 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) The K13 terminal functions as the clock input terminal for the programmable timer, and the input
signal is shared with the input port and the programmable timer. Therefore, when the K13 terminal is
set to the clock input terminal for the programmable timer, take care of the interrupt setting.
(3) After an interrupt occurs, the same interrupt will occur again if the interrupt enabled state (I flag =
"1") is set or the RETI instruction is executed unless the interrupt factor flag is reset. Therefore, be sure
to reset (write "1" to) the interrupt factor flag in the interrupt service routine before shifting to the
interrupt enabled state.
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EPSON
S1C63558 TECHNICAL MANUAL