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10 REAL-TIME CLOCK (RTCA)
S1C31D50/D51 TECHNICAL MANUAL
Seiko Epson Corporation
10-11
(Rev. 2.00)
Bits 6–4
RTCMIH[2:0]
Bits 3–0
RTCMIL[3:0]
The RTCAHUR.RTCMIH[2:0] bits and the RTCAHUR.RTCMIL[3:0] bits are used to set and read
the 10-minute digit and the 1-minute digit of the minute counter, respectively. The setting/read values
are a BCD code within the range from 0 to 59.
Note: Be sure to avoid writing to the RTCAHUR.RTCMIH[2:0]/RTCMIL[3:0] bits while the RT-
CACTLL.RTCBSY bit = 1.
RTCA Month/Day Register
Register name
Bit
Bit name
Initial
Reset
R/W
Remarks
RTCAMON
15–13 –
0x0
–
R
–
12 RTCMOH
0
H0
R/W
11–8 RTCMOL[3:0]
0x1
H0
R/W
7–6 –
0x0
–
R
5–4 RTCDH[1:0]
0x0
H0
R/W
3–0 RTCDL[3:0]
0x1
H0
R/W
Bits 15–13 Reserved
Bit 12
RTCMOH
Bits 11–8 RTCMOL[3:0]
The RTCAMON.RTCMOH bit and the RTCAMON.RTCMOL[3:0] bits are used to set and read the
10-month digit and the 1-month digit of the month counter, respectively. The setting/read values are a
BCD code within the range from 1 to 12.
Notes: • Be sure to avoid writing to the RTCMON.RTCMOH/RTCMOL[3:0] bits while the RTCCTL.
RTCBSY bit = 1.
• Be sure to avoid setting the RTCMON.RTCMOH/RTCMOL[3:0] bits to 0x00.
Bits 7–6
Reserved
Bits 5–4
RTCDH[1:0]
Bits 3–0
RTCDL[3:0]
The RTCAMON.RTCDH[1:0] bits and the RTCAMON.RTCDL[3:0] bits are used to set and read the
10-day digit and the 1-day digit of the day counter, respectively. The setting/read values are a BCD
code within the range from 1 to 31 (to 28 for February in a common year, to 29 for February in a leap
year, or to 30 for April/June/September/November).
Note: Be sure to avoid writing to the RTCAMON.RTCDH[1:0]/RTCDL[3:0] bits while the RT-
CACTLL.RTCBSY bit = 1.
RTCA Year/Week Register
Register name
Bit
Bit name
Initial
Reset
R/W
Remarks
RTCAYAR
15–11 –
0x00
–
R
–
10–8 RTCWK[2:0]
0x0
H0
R/W
7–4 RTCYH[3:0]
0x0
H0
R/W
3–0 RTCYL[3:0]
0x0
H0
R/W
Bits 15–11 Reserved
Bits 10–8 RTCWK[2:0]
These bits are used to set and read day of the week.
The day of the week counter is a base-7 counter and the setting/read values are 0x0 to 0x6. Table 10.6.2
lists the correspondence between the count value and day of the week.