Specifications

S1C62N82 TECHNICAL HARDWARE EPSON I-35
CHAPTER 4: PERIPHERAL CIRCUITS AND OPERATION (Input Ports)
Note
Reading of interrupt factor flags is available at EI, but be
careful in the following cases.
If the interrupt mask register value corresponding to the
interrupt factor flags to be read is set to 1, an interrupt
request will be generated by the interrupt factor flags set
timing, or an interrupt request will not be generated.
Be very careful when interrupt factor flags are in the same
address.
After an initial reset, these flags are set to 0.
- When input ports are changed from high to low by pull-down
resistance, the fall of the waveform is delayed on account of the
time constant of the pull-down resistance 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. Aim for a wait time of about 1 ms.
- When "Use" (noise rejector enable) is selected with the mask
option, a maximum delay of 1 ms occurs from time the interrupt
conditions are established until the interrupt factor flag (IK) is
set to 1 (until the interrupt is actually generated).
Hence, pay attention to the timing when reading out (resetting)
the interrupt factor flag.
For example, when performing a key scan with the key matrix,
the key scan changes the input status to set the interrupt factor
flag, so it has to be read out to reset it. However, if the interrupt
factor flag is read out immediately after key scanning, the delay
will cause the flag to be set after read-out, so that it will not be
reset.