WATCHDOG TIMER V1.1
Chapter 4 Usage and Examples
MCU-AN-500013-E-11 – Page 9
4 Usage and Examples
Functions and examples for watchdog timer
This section describes the usage of watchdog timer and gives some examples.
4.1 Functions and Operations of watchdog timer
Please write certain values to NVR flash area address FFBE
H
and FFBF
H
to choose the
watchdog timer operation mode. See Table 2-1 for detailed settings of mode choose.
The Watchdog Timer has two operate modes as below:
Software watchdog
1) Write “A596
H
” (enable software watchdog timer) to the address FFBE
H
and
FFBF
H
on the flash memory, which are copied to the watchdog timer selection
ID register WDTH/WDTL (0FEB
H
/0FEC
H
) after a reset.
2) The watchdog timer is activated when “0101B” is written to the watchdog
control bits of the watchdog timer control register (WDTC: WTE3 to WTE0) for
the first time after a reset. The count clock switch bits of the watchdog timer
register (WDTC: CS1, CS0, CSP) should also be set at the same time.
3) Once the watchdog timer is activated, a reset is the only way to stop its
operation. Please clear watchdog counter in a specified intervals regularly
depend on the setting of WDTC: CS1, CS0, CSP. Refer to Table 3-1 for
detailed interval time.
Hardware watchdog
1) Write “A597
H
” (WDT can be stopped in a standby mode) or any other value
(WDT is enabled in every mode) except than “A596
H
” or “A597
H
” to the
address FFBE
H
and FFBF
H
on the flash memory, which are copied to the
watchdog timer selection ID register WDTH/WDTL (0FEB
H
/0FEC
H
) after a
reset.
2) The hardware watchdog timer starts automatically after a reset and cannot be
stopped. Please clear its counter at specified intervals regularly to avoid
generates a watchdog timer reset.
3) This timer is cleared by reset and resumes operation after the reset.
Please note that the watchdog timer is cleared at the same time as the timer selected as the
count clock (timebase timer or watch prescaler) is cleared. For this reason, the watchdog
timer cannot function as such, if the software is set to clear the selected timer repeatedly
during the interval time of the watchdog timer
