Datasheet

Section 14 Watchdog Timer (WDT)
Rev. 4.00 Sep 27, 2006 page 422 of 1130
REJ09B0327-0400
Caution is therefore required when using WDT1 as the realtime clock counter.
No error occurs in the counter value while WDT1 is operating in the same mode.
14.5.6 OVF Flag Clear Condition
To clear OVF flag in WOVI handling routine, read TCSR when OVF = 1, then write with 0 to
OVF, as stated above. When WOVI is masked and OVF flag is poling, if contention between OVF
flag set and TCSR read is occurred, OVF = 1 is read but OVF can not be cleared by writing with 0
to OVF.
In this case, reading TCSR when OVF = 1 two times meet the requirements of OVF clear
condition. Please read TCSR when OVF = 1 two times before writing with 0 to OVF.
LOOP BTST.B #7, @TCSR ; OVF flag read
BEQ LOOP ; if OVF=1, exit from loop
MOV.B @TCSR, R0L ; OVF=1 read again
MOV.W #H'A521, R0 ; OVF flag clear
MOV.W R0,@TCSR ; :