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TCNT count
H'00
Time
H'FF
WT/ =0
TME=1
WOVI
Overflow
Overflow
Overflow
Overflow
Legend
WOVI: Interval timer interrupt request generation
WOVI
WOVI
WOVI
Figure 14.3 Operation in Interval Timer Mode
14.5
Interrupts
During interval timer mode operation, an overflow generates an interval timer interrupt (WOVI).
The interval timer interrupt is requested whenever the OVF flag is set to 1 in TCSR. OVF must be
cleared to 0 in the interrupt handling routine.
Table 14.2
WDT Interrupt Source
Name
Interrupt Source
Interrupt Flag
DTC Activation
WOVI
TCNT overflow
OVF
Impossible
14.6
Usage Notes
14.6.1
Notes on Register Access
The watchdog timer’s TCNT, TCSR, and RSTCSR registers differ from other registers in being
more difficult to write to. The procedures for writing to and reading these registers are given
below.
Writing to TCNT, TCSR, and RSTCSR
TCNT and TCSR must be written to by a word transfer instruction. They cannot be written to by a
byte transfer instruction.
TCNT and TCSR both have the same write address. Therefore, satisfy the relative condition
shown in figure 14.4 to write to TCNT or TCSR. The transfer instruction writes the lower byte
data to TCNT or TCSR according to the satisfied condition.
Содержание H8S/2376 F-ZTAT
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