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1 how do i set the count period of 1 second, 2 how do i initialize real-time clock, 3 how do i set or update time (hour/minute/second) – FUJITSU MB91460 SERIES FR60 User Manual

Page 975: 5 how do i confirm that real-time clock is active, 6 how do i know time, 7 how do i stop real-time clock, Q&a 7.1 how do i set the count period of 1 second

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Chapter 49 Real-Time Clock

7.Q&A

7. Q&A

7.1 How do I set the count period of 1 second?

Stop Real-time Clock and then set the sub-second register WTBR. The reload value corresponds to the time
needed for half a second, i.e.

• At 32 kHz RTC operation set WTBR to “001FFF

H

”.

• At 100 kHz RTC operation set WTBR to “0061A7

H

”.

• At 4 MHz RTC operation set WTBR to “0F423F

H

”.

7.2 How do I initialize Real-time Clock?

Use the start bit (WTCR.ST).

Changing the start bit from “1” to “0” resets the hour/minute/second counters and the 21 bit down counter
to “0” (initialization), and stops count operation.

7.3 How do I set or update time (hour/minute/second)?

Write values to the hour/minute/second registers, WTHR/WTMR/WTSR, and set the update bit (UPDT).

7.4 How do I start or stop Real-time Clock's counting?

Use the start bit (WTCR.ST).

7.5 How do I confirm that Real-time Clock is active?

Use the run flag (WTCR.RUN).

7.6 How do I know time?

Read the hour/minute/second registers, 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 (SS) => 03:59:59 (SS) => 03:00:00

Read begins at the hour register: 02:59:59 => 02:00:00 => 03:00:00

7.7 How do I stop Real-time Clock?

See 7.4.

Operation

Update bit (UPDT)

To update the hour/minute/second counters

Set the bit to “1”.

Operation

Start bit (ST)

To stop Real-time Clock's counting

Set the bit to “0”.

To start Real-time Clock's counting

Set the bit to “1”.

Operation

Run flag (RUN)

Real-time Clock is inactive.

The flag is set to “0”.

Real-time Clock is active.

The flag is set to “1”.