
III PERIPHERAL MODULES 1 (SYSTEM): REAL-TIME CLOCK (RTC)
S1C33E07 TECHNICAL MANUAL
EPSON
III-3-3
III
RTC
1-day counter
This 4-bit BCD counter counts in units of days. It counts from 0 to 9 with 1 carried over from the hour counter.
This counter is reset to 0 after 9 and outputs a carry over of 1 to the 10-day counter. The number of days in each
month and leap years are taken into account, so that the counter is reset to 1 when months change. The count
data is read out and written using RTCDL[3:0] (D[3:0]/0x30191C).
RTCDL[3:0]: RTC 1-day Counter Bits in the RTC Day Register (D[3:0]/0x30191C)
10-day counter
This 2-bit BCD counter counts tens of days. It counts from 0 to 2 or 3 with 1 carried over from the 1-day
counter. The number of days in each month and leap years are taken into account, so that when months change
the counter is reset to 0 along with the 1-day counter, and outputs a carry over of 1 to the 1-month counter. The
count data is read out and written using RTCDH[1:0] (D[5:4]/0x30191C).
RTCDH[1:0]: RTC 10-day Counter Bits in the RTC Day Register (D[5:4]/0x30191C)
1-month counter
This 4-bit BCD counter counts in units of months. It counts from 0 to 9 with 1 carried over from the day
counter. This counter is reset to 0 after 9 and outputs a carry over of 1 to the 10-month counter. The counter is
reset to 1 when years change. The count data is read out and written using RTCMOL[3:0] (D[3:0]/0x301920).
RTCMOL[3:0]: RTC 1-month Counter Bits in the RTC Month Register (D[3:0]/0x301920)
10-month counter
This counter counts in units of 10 months, and is set to 1 with 1 carried over from the 1-month counter. When
years change, this counter is reset to 0 along with the 1-month counter, and outputs a carry over of 1 to the
1-year counter. The count data is read out and written using RTCMOH (D4/0x301920).
RTCMOH: RTC 10-month Counter Bit in the RTC Month Register (D4/0x301920)
1-year counter
This 4-bit BCD counter counts in units of years. It counts from 0 to 9 with 1 carried over from the month
counter. This counter is reset to 0 after 9 and outputs a carry over of 1 to the 10-year counter. The count data is
read out and written using RTCYL[3:0] (D[3:0]/0x301924).
RTCYL[3:0]: RTC 1-year Counter Bits in the RTC Year Register (D[3:0]/0x301924)
10-year counter
This 4-bit BCD counter counts tens of years. It counts from 0 to 9 with 1 carried over from the 1-year counter.
The count data is read out and written using RTCYH[3:0] (D[7:4]/0x301924).
RTCYH[3:0]: RTC 10-year Counter Bits in the RTC Year Register (D[7:4]/0x301924)
Days of week counter
This is a septenary counter (that counts from 0 to 6) representing the days of the week. It counts with the same
timing as the 1-day counter. The count data is read out and written using RTCWK[2:0] (D[2:0]/0x301928).
RTCWK[2:0]: RTC Days of Week Counter Bits in the RTC Days of Week Register (D[2:0]/0x301928)
The correspondence between the counter values and days of the week can be set in a program as desired. Table
III.3.2.1 lists the basic correspondence.
Table III.3.2.1 Correspondence between Counter Values and Days of the Week
RTCWK2
1
0
RTCWK1
1
0
1
0
Days of the week
Saturday
Friday
Thursday
Wednesday
Tuesday
Monday
Sunday
RTCWK0
0
1
0
1
0
1
0