8 REAL-TIME CLOCK (RTC)
8-16
Seiko Epson Corporation
S1C17624/604/622/602/621 TECHNICAL MANUAL
D[7:4] RTCYH[3:0]: RTC 10-year Counter Bits
These bits comprise a 4-bit BCD counter used to count tens of years. The counter counts from 0 to 9
with a carry over of 1 from the 1-year counter.
D[3:0] RTCYL[3:0]: RTC 1-year Counter Bits
These bits comprise a 4-bit BCD counter used to count units of years.
The counter counts from 0 to 9 with a carry over of 1 from the month counter. This counter is reset to 0
after 9 and outputs a carry over of 1 to the 10-year counter.
RTC Days of Week Register (RTC_WEEK)
Register name Address Bit Name Function Setting Init. R/W Remarks
RTC Days of
Week Register
(RTC_WEEK)
0x514a
(8 bits)
D7–3
–
reserved – – – 0 when being read.
D2–0
RTCWK[2:0]
RTC days of week counter RTCWK[2:0]
Days of week
X (*) R/W
0x7
0x6
0x5
0x4
0x3
0x2
0x1
0x0
–
Saturday
Friday
Thursday
Wednesday
Tuesday
Monday
Sunday
* Software reset (RTCRST → 1 → 0) does not affect the counter values. This register retains the value set before a software reset is
performed.
Notes: • Data should not be read from or written to the counters while 1 is being carried over. (See
Section 8.3.5, “Counter Hold and Busy Flag,” and Section 8.3.7, “Counter Read.”)
• Rewriting RTC24H/RTC_CNTL0 register may corrupt the count data in this register. Therefore,
after changing the RTC24H setting, be sure to set up this register again.
D[7:3] Reserved
D[2:0] RTCWK[2:0]: RTC Days of Week Counter Bits
This is a septenary counter (that counts from 0 to 6) representing days of the week. This counter counts
at the same timing as t
he 1-day counter.
The correspondence between the counter values and days of the week can be set in a program as de-
sired. Table 8.5.3 lists the basic correspondence.
5.3 Correspondence between Counter Values and Days of the WeekTable 8.
RTCWK[2:0] Days of the week
0x6 Saturday
0x5 Friday
0x4 Thursday
0x3 Wednesday
0x2 Tuesday
0x1 Monday
0x0 Sunday
(Default: indeterminate, software reset: previous value retained)
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