R01UH0823EJ0100 Rev.1.00 Page 207 of 1823
Jul 31, 2019
RX23W Group 9. Clock Generation Circuit
When using the sub-clock only as the count source of the realtime clock, perform initial settings according to the
flowchart example shown in
Figure 9.15. After that, perform the clock setting procedure shown in section 28.3.2,
Clock and Count Mode Setting Procedure
.
Figure 9.15 Example of Initialization Flowchart When Sub-Clock is Used Only as Count Source of Realtime
Clock
Start
Set the SOSCCR.SOSTP bit to 1 (sub-clock oscillator is stopped).
Read the SOSCCR.SOSTP bit and confirm that it is 1.
Set the RCR3.RTCEN bit to 0 (sub-clock oscillator is stopped).
Read the RCR3.RTCEN bit and confirm that it is 0.
*1
Wait for at least five cycles (about 153 µs) of the sub-clock to elapse.
Set bit 3 to bit 1 in the RCR3 register (or the RCR3.RTCDV[2:0] bits) to
001b or 110b.
Read bit 3 to bit 1 in the RCR3 register (or the RCR3.RTCDV[2:0] bits) and
confirm that they have been rewritten.
Wait for the oscillation stabilization time of the sub-clock to elapse by software.
Set the RCR3.RTCEN bit to 1 (sub-clock oscillator is operating).
Read the RCR3.RTCEN bit and confirm that it is 1.
End
Sub-clock
oscillation state
Stopped
Oscillating
SOSCCR.
SOSTP
RCR3.
RTCEN
0
Undefined
0
1
1
Note 1. The values of bit 7 to bit 1 are undefined. Confirm only the value of the RCR3.RTCEN bit.
Oscillating
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