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Chapter 20 Software Watchdog Timer
5.Operation
5. Operation
This section describes the watchdog operation.
5.1 Watchdog (Detecting Runaway)
(1) Setting interval time
(2) Watchdog startup (Watchdog timer clear)
(3) Interval signal output from the timebase counter. The watchdog timer counts.
(4) Within the interval time, by software periodic writing to the WPR register with “A5” and “5A” has been performed.
The watchdog timer clears.
(5) Within the interval time, by software periodic writing to the WPR register with “A5” and “5A” has been performed.
The watchdog timer clears.
(6) Interval signal output from the timebase counter. The watchdog timer counts.
(7) Within the interval time, by software periodic writing to the WPR register with “A5” and “5A” has been performed.
Watchdog timer clears.
(8) Interval signal output from the timebase counter. The watchdog timer counts.
(9) MCU runs away (the runaway of MCU is assumed).
(10) Within interval time, by software writing to the WPR register with “A5” and “5A” has not been performed.
(11) Interval signal output from the timebase counter. The watchdog timer counts.
(12) Runaway is detected, WODOG flag has been changed to “1”.
(13) Watchdog reset (INIT) has been generated.
Interval period
selection
Runaway
detection
(3)
Reading from the RSRR
register
(2)
(7)
(9)
WDOG bit
(3)
(4)
(6)
Count value of
the timer counter
(5)Watchdog timer
Periodically writing
“A5” and “5A” in the
WPR register
Setting initialization reset
(INIT)
Clear by
software
Clear by
software
Clear by
software
With
no clear
Normal operation Runaway Reset
Watchdog
startup
(1)
(4)
(5)
(6)
(7)
(8)
(8)
(10)
(11)
(12)
(12)
(13)
Bit output of
the timer counter
(Bits 15, 17, 19 and 21)
(8)
(6)
(3)