
S1C62N82 TECHNICAL SOFTWARE
EPSON
II-91
CHAPTER 4: SUMMARY OF PROGRAMMING POINTS
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. 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 4.1. In this case, when the mask regis-
ters 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 input comparison register is rewritten in the input
terminal active status, an input interrupt factor flag may
be set. Thus, you should rewrite the content of the input
comparison register in the mask register = "0" status.
Output Port
The FOUT output signal may produce hazards when the
output port R10 is turned on or off.
I/O Port
– When the I/O port is set to the output mode and a low-
impedance load is connected to the port pin, the data
written to the register may differ from the data read.
– When the I/O port is set to the input mode and a low-
level voltage (VSS) is input by the built-in pull-down
resistance, an erroneous input results if the time con-
stant of the capacitive load of the input line and the built-
in pull-down resistance load is greater than the read-out
time. When the input data is being read, the time that the
input line is pulled down is equivalent to 0.5 cycles of the
CPU system clock.
Hence, the electric potential of the pins must settle within
0.5 cycles. If this condition cannot be met, some measure
must be devised, such as arranging a pull-down resis-
tance externally, or performing multiple read-outs.