Toshiba TLCS-900/H1 Series Manual page 330

(2) Writing clock data
When a carry over occurs during a write operation, the data cannot be written correctly.
Please use the following method to ensure data is written correctly.
1. Using 1Hz interrupt
1Hz interrupt and the count up of internal data synchronize. Therefore, data
can write correctly if writing data after 1Hz interrupt occurred.
2. Resetting a counter
There are 15-stage counter inside the RTC, which generate a 1Hz clock from
32,768 kHz. The data is written after reset this counter.
However, if clearing the counter, it is counted up only first writing at half of the
setting time, first writing only. Therefore, if setting the clock counter correctly,
after clearing the counter, set the 1Hz-interrupt to enable. And set the time after
the first interrupt (occurs at 0.5s) is occurred.
Figure 3.13.3 Flowchart of data write
Start
PAGER<PAGE> = "0" ,
Select PAGE0
RESTR<RSTTMR> = "1"
reset counter
RESTR<DIS1HZ> = "0"
enable 1Hz interrupt
First interrupts occur
(After 0.5s)
YES
Sets the time
END
92CH21-328
TMP92CH21
NO
2009-06-19