
iiiPeriPheraLModuLes1(systeM):reaL-tiMeCLoCk(rtC)
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iii-3-21
III
RTC
0x301918:rtChourregister(prtChour)
name
address
registername
Bit
Function
setting
init. r/W
remarks
–
rtCaP
rtChh1
rtChh0
rtChL3
rtChL2
rtChL1
rtChL0
D31–7
D6
D5
D4
D3
D2
D1
D0
reserved
AM/PMindicator
RTC10-hourcounter
RTC1-hourcounter
–
X
–
R/W
0whenbeingread.
00301918
(W)
rtChour
register
(pRTCHOUR)
0to2or0to1
–
1 PM
0 AM
0to9
notes: Data should not be read from or written to the counters while 1 is being carried over. (See
Section III.3.3.5,“Counter Hold and Busy Flag,” and Section III.3.3.6,“Reading from and
WritingtoCountersinOperation.”)
RewritingRTC24H(D4/0x301908)maycorruptthecountdatainthisregister.Therefore,after
changingtheRTC24H(D4/0x301908)setting,besuretosetupthisregisteragain.
d[31:7] reserved
d6
rtCaP:aM/PMindicatorBit
When 12-hour mode is selected, this bit indicates A.M. or P.M.
1 (R/W): P.M.
0 (R/W): A.M.
This bit is only effective when RTC24H (D4/0x301908) is set to 0 (12-hour mode).
When 24-hour mode is selected, this bit is fixed to 0. In this case, do not write 1 to RTCAP.
note: TheRTCAPbitkeepsthecurrentsetvalueevenifRTC24H(D4/0x301908)ischangedfrom
12-hourmodeto24-hourmode,andwillbefixedat0afterthehourcounterisupdated(or
resetinsoftware).
d[5:4]
rtChh[1:0]:rtC10-hourCounterBits
These bits comprise a 2-bit BCD counter used to count tens of hours.
With a carry over of 1 from the 1-hour counter, the counter counts from 0 to 1 when 12-hour mode is
selected, or from 0 to 2 when 24-hour mode is selected. The counter is reset at 12 o’clock or 24 o’clock,
and outputs a carry over of 1 to the 1-day counter.
d[3:0]
rtChL[3:0]:rtC1-hourCounterBits
These bits comprise a 4-bit BCD counter used to count units of hours.
The counter counts from 0 to 9 with a carry over of 1 from the 10-minute counter. This counter is reset
to 0 after 9 and outputs a carry over of 1 to the 10-hour counter. Depending on whether 12-hour mode
or 24-hour mode is selected, the counter is reset at 12 o’clock or 24 o’clock.