I-116
EPSON
S1C62740 TECHNICAL HARDWARE
CHAPTER 5: SUMMARY OF NOTES
When in the input mode, I/O ports are changed from low to high
by pull up resistor, the rise of the waveform is delayed on account
of the time constant of the pull up resistor 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.
Make this waiting time the amount of time or more calculated by
the following expression.
10
× C × R
C: terminal capacitance 5 pF + parasitic capacitance ? pF
R: pull up resistance 300 k
I/O ports
LCD driver (1) The contents of the display memory are undefined until the area
is initialized (through, for instance, memory clear processing by
the CPU). Initialize the display memory by executing initial
processing.
(2) Since the display memory area is write-only, display data
cannot be rewritten by arithmetic operations (such as AND, OR,
ADD, SUB).
Clock timer (1) Be sure to data reading in the order of low-order data (TM0–
TM3) then high-order data (TM4–TM7).
(2) When the clock timer has been reset, the interrupt factor flag
(IT) may sometimes be set to "1". Consequently, perform flag
reading (reset the flag) as necessary at reset.
(3) When the clock timer has been reset, the watchdog timer is also
reset.
Stopwatch timer (1) Be sure to data reading in the order of low-order data (SWL0–
SWL3) then high-order data (SWH0–SWH3).
(2) When the stopwatch timer has been reset, the interrupt factor
flag (ISW) may sometimes be set to "1". Consequently, perform
flag reading (reset the flag) as necessary at reset.
Programmable timer (1) Be sure to data reading in the order of low-order data (PT0–PT3)
then high-order data (PT4–PT7).
(2) When data of reload registers is set at "00H", the down-counter
becomes a 256-value counter.
Serial interface (1) When using the serial interface in the master mode, the syn-
chronous clock uses the CPU system clock. Accordingly, do not
change the system clock (fOSC1
fOSC3) while the serial inter-
face is operating.