I-158
EPSON
S1C62440/624A0/624C0/62480 TECHNICAL HARDWARE
CHAPTER 15: SUMMARY OF NOTES
(1) When changing the input port from Low level to High
level with a pull up resistor, a delay in the waveform rise
time will occur depending on the time constant of the pull
up resistor and input gate capacity. Hence, when reading
data from the input port, set an appropriate waiting time.
Care is particularly required for key matrix configuration
scanning. For reference, approximately 500 s waiting
time is required.
(2) Input interrupt programing related precautions
Input port
(Kxx)
When the content of the mask register is rewritten, while the port K
input is in the active status. The input interrupt factor flags are set at
and , being the interrupt due to the falling edge and the
interrupt due to the rising edge.
When using an input interrupt, if you rewrite the content
of the mask register, when the value of the input terminal
which becomes the interrupt input is in the active status,
the factor flag for input interrupt may be set. Therefore,
when using the input interrupt, the active status of the
input terminal implies
input terminal = Low status, when the falling edge
interrupt is effected and
input terminal = High status, when the rising edge
interrupt is effected.
When an interrupt is triggered at the falling edge of an
input terminal, a factor flag is set with the timing of
shown in Figure 15.2.1. However, when clearing the
content of the mask register with the input terminal kept
in the Low status and then setting it, the factor flag of the
input interrupt is again set at the timing that has been
set.
Consequently, when the input terminal is in the active
status (Low status), do not rewrite the mask register
(clearing, then setting the mask register), so that a factor
flag will only set at the falling edge in this case.
Fig. 15.2.1
Input interrupt timing
Port K input
Factor flag set Not set
Factor flag set
Input relation
register
Mask register
Active status
Rising edge interrupt
Falling edge interrupt