Toshiba H1 Series Data Book page 588

(3) Writing timer data
When there is carry on the way of write operation, expecting data can not be wrote
exactly. Therefore, in order to write in data exactly please follow the below way.
1. Resetting a divider
In RTC inside, there are 15-stage dividers, which generates 1Hz clock from
32,768 KHz. Carry of a timer is not done for one second when reset this divider. So
write in data at this interval.
Figure 3.21.4 Flowchart of data write
Start
PAGER<PAGE> = "0"
Select PAGE0
RESTR<RSTTMR> = "1"
Divider reset
Write the clock data
End
92CZ26A-585
TMP92CZ26A
Note)
This period is within
0.5 secound.