9 REAL-TIME CLOCK (RTCA)
9-8
Seiko Epson Corporation
S1C17M20/M21/M22/M23/M24/M25
TECHNICAL MANUAL (Rev. 1.0)
Table 9.6.1 Setting Examples in BCD Code
Setting value in BCD code
Alarm (second) setting
RTCALM1.RTCSHA[2:0] bits
RTCALM1.RTCSLA[3:0] bits
0x0
0x0
00 seconds
0x0
0x1
01 second
· · ·
· · ·
· · ·
0x0
0x9
09 seconds
0x1
0x0
10 seconds
· · ·
· · ·
· · ·
0x5
0x9
59 seconds
Bits 7–0
Reserved
RTC Hour/Minute Alarm Register
Register name
Bit
Bit name
Initial
Reset
R/W
Remarks
RTCALM2
15 –
0
–
R
–
14 RTCAPA
0
H0
R/W
13–12 RTCHHA[1:0]
0x0
H0
R/W
11–8 RTCHLA[3:0]
0x0
H0
R/W
7
–
0
–
R
6–4 RTCMIHA[2:0]
0x0
H0
R/W
3–0 RTCMILA[3:0]
0x0
H0
R/W
Bit 15
Reserved
Bit 14
RTCAPA
This bit sets A.M. or P.M. of the alarm time in 12H mode (RTCCTL.RTC24H bit = 0).
1 (R/W): P.M.
0 (R/W): A.M.
This setting is ineffective in 24H mode (RTCCTL.RTC24H bit = 1).
Bits 13–12 RTCHHA[1:0]
Bits 11–8 RTCHLA[3:0]
The RTCALM2.RTCHHA[1:0] bits and the RTCALM2.RTCHLA[3:0] bits set the 10-hour digit and
1-hour digit of the alarm time, respectively. A value within 1 to 12 o’clock in 12H mode or 0 to 23 in
24H mode can be set in BCD code.
Bit 7
Reserved
Bits 6–4
RTCMIHA[2:0]
Bits 3–0
RTCMILA[3:0]
The RTCALM2.RTCMIHA[2:0] bits and the RTCALM2.RTCMILA[3:0] bits set the 10-minute digit
and 1-minute digit of the alarm time, respectively. A value within 0 to 59 minutes can be set in BCD
code.
RTC Stopwatch Control Register
Register name
Bit
Bit name
Initial
Reset
R/W
Remarks
RTCSWCTL
15–12 BCD10[3:0]
0x0
H0
R
–
11–8 BCD100[3:0]
0x0
H0
R
7–5 –
0x0
–
R
4
SWRST
0
H0
W
Read as 0.
3–1 –
0x0
–
R
–
0
SWRUN
0
H0
R/W
Bits 15–12 BCD10[3:0]
Bits 11–8 BCD100[3:0]
The 1/10-second and 1/100-second digits of the stopwatch counter can be read as a BCD code from
the RTCSWCTL.BCD10[3:0] bits and the RTCSWCTL.BCD100[3:0] bits, respectively.