R01UH0823EJ0100 Rev.1.00
Page 805 of 1823
Jul 31, 2019
RX23W Group
28. Realtime Clock (RTCe)
28.6.4
Transitions to Low Power Consumption Modes after Setting Registers
A transition to a low power consumption state (software standby mode, or battery backup) during writing to or updating
of an RTC register might destroy the register’s value. After setting a register, confirm that the setting is in place before
initiating a transition to a low power consumption state.
28.6.5
Notes When Writing to and Reading from Registers
When reading a counter register such as the second counter after having written to the counter register, follow the
procedure in
section 28.3.5, Reading 64-Hz Counter and Time
.
The value written to the count registers, alarm registers, year alarm enable register, bits RCR2.AADJE, AADJP, and
HR24, or RCR3 register is reflected when four read operations are performed after writing.
The values written to the RCR1.CIE, RTCOS, and RCR2.RTCOE bits can be read immediately after writing.
To read the value from the timer counter after return from a reset, software standby mode, or the battery backup
state, wait for 1/128 second while the clock is operating (RCR2.START bit = 1).
After a reset is generated, write to the RTC register when six cycles of the count source have elapsed.
28.6.6
Changing the Count Mode
When changing the count mode (calendar/binary), set the RCR2.START bit to 0, stop counting operation, then start again
from the initial setting. For details on initial setting, refer to
section 28.3.1, Outline of Initial Settings of Registers
.
