
S1C62N33 TECHNICAL SOFTWARE
EPSON
II-81
CHAPTER 5: PERIPHERAL CIRCUITS (Input Ports)
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 5.7.3. 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 regis-
ter (clearing, then setting the mask register), so that a
factor flag will only set at the falling edge in this case.
When clearing, then setting the mask register, set the
mask register, when the input terminal is not in the
active status (high status).
When an interrupt is triggered at the rising edge of the
input terminal, a factor flag will be set at the timing of
shown in Figure 5.7.3. In this case, when the mask
registers cleared, then set, you should set the mask
register, when the input terminal is in the low status.
In addition, when the mask register = "1" and the content
of the differential register is rewritten in the input termi-
nal active status, an input interrupt factor flag may be
set. Thus, you should rewrite the content of the differen-
tial register in the mask register = "0" status.
(5) Read out the interrupt factor flag (IK) only in the DI
status (interrupt flag = "0"). Read-out during EI status
can cause an error.
(6) Even when the values of the input data and differential
register changes from non-matching to matching, the
interrupt factor flag is not set to "1".
(7) Since the SCTRG/SIOF registers are at 77H, care needs
to be taken when using operational commands (AND, OR,
ADD, SUB, etc.).