Epson S1C6S3N2, Technical Manual

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S1C6S3N2 TECHNICAL HARDWARE
EPSON
I-99
CHAPTER 5: SUMMARY OF NOTES
(2) When "noise rejector circuit enable" is selected with the
mask option, a maximum delay of 1 ms occurs from the
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, immedi-
ately after performing a key scan with the key matrix, the
flag will not be reset because the delay in the interrupt
factor flag read-out means the flag is set after read-out.
(The key scan changes the input status and the interrupt
factor flag is set, necessitating read-out to reset the flag.)
(3) Input interrupt programing related precautions
Fig. 5.2.1
Input interrupt timing
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
➀
and
➁
,
➀
being the interrupt due to the falling edge and
➁
the interrupt due to the rising edge.
Port K input
Factor flag set Not set
➁
Factor flag set
Differential register
Mask register
Active status Active status
Rising edge interrupt
➀
Falling edge interrupt
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
➀
shown in Figure 5.2.1. 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.