131
CHAPTER 6 WATCHDOG TIMER
6.4
Operations of Watchdog Timer Functions
The watchdog timer generates a watchdog reset when the watchdog timer counter
overflows.
■
Operations of Watchdog Timer
●
Activating watchdog timer
The watchdog timer is activated when the first time "0101
B
" is written to the watchdog control bits
(WDTC: WTE3 to WTE0) of the watchdog control register.
The watchdog timer cannot be stopped without accepting a reset upon activation.
●
Clearing watchdog timer
The watchdog timer counter is cleared the second or subsequent time "0101
B
" is written to the watchdog
control bits (WDTC: WTE3 to WTE0) of the watchdog control register.
When the counter is not cleared within the time interval of the watchdog timer, the counter overflows and
the timer generates the internal reset signal having a period of four instruction cycles.
●
Time intervals of watchdog timer
The time interval varies depending on the timing at which the watchdog timer is cleared. Figure 6.4-1
shows the relationship between the clear timings and time intervals of the watchdog timer when output
from the time-base timer is used as the count clock (oscillation frequency: 12.5 MHz).
Figure 6.4-1 Clearing Watchdog Timer and Time Interval
671.0 m
s
33
5.5 m
s
Minim
u
m time interv
a
l
Co
u
nt clock o
u
tp
u
t from
time-
bas
e timer
W
a
tchdog cle
a
r
Overflow
W
a
tchdog 1-
b
it co
u
nter
W
a
tchdog re
s
et
M
a
xim
u
m time interv
a
l
Co
u
nt clock o
u
tp
u
t from
time-
bas
e timer
W
a
tchdog cle
a
r
Overflow
W
a
tchdog 1-
b
it co
u
nter
W
a
tchdog re
s
et
Summary of Contents for F2MC-8L F202RA
Page 2: ......
Page 4: ......
Page 32: ...16 CHAPTER 1 OVERVIEW ...
Page 90: ...74 CHAPTER 3 CPU ...
Page 142: ...126 CHAPTER 5 TIME BASE TIMER POPW A RETI ENDS END ...
Page 150: ...134 CHAPTER 6 WATCHDOG TIMER ...
Page 176: ...160 CHAPTER 7 8 BIT PWM TIMER ...
Page 220: ...204 CHAPTER 8 8 16 BIT CAPTURE TIMER COUNTER ...
Page 240: ...224 CHAPTER 9 12 BIT PPG TIMER ...
Page 274: ...258 CHAPTER 11 EXTERNAL INTERRUPT CIRCUIT 2 LEVEL ...
Page 362: ...346 CHAPTER 15 BUZZER OUTPUT ...
Page 390: ...374 CHAPTER 17 FLASH MEMORY ...
Page 419: ...403 INDEX INDEX The index follows on the next page This is listed in alphabetic order ...
Page 434: ...418 INDEX ...
Page 436: ......