FUJITSU MB91460 SERIES FR60 - Manual (Page 978)

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Chapter 49 Real-Time Clock
8.Caution
lower than that of the peripheral clock (CLKP). If not, correct values cannot be read from WTHR/WTMR/
WTSR.
• Note that only byte-access is allowed to these register. So, when these registers are read at the very timing
of changing over the hour or minute boundary as shown below, there is a possibility of misjudging the time.
So, read several times to get a logically consistent value.
Example: Read begins at the second register: 02:59:59=> 03:59:59 => 03:00:00
Read begins at the hour register: 02:59:59 => 02:00:00 => 03:00:00
In this case, the current time should be interpreted as 3 o'clock.