10 REAL-TIME CLOCK (RTCA)
S1C31D50/D51 TECHNICAL MANUAL
Seiko Epson Corporation
10-1
(Rev. 2.00)
10 Real-Time Clock (RTCA)
10.1 Overview
RTCA is a real-time clock with a perpetual calendar function. The main features of RTCA are outlined below.
• Includes a BCD real-time clock counter to implement a time-of-day clock (second, minute, and hour) and calen-
dar (day, day of the week, month, and year with leap year supported).
• Provides a hold function for reading correct counter values by suspending the real-time clock counter operation.
• 24-hour or 12-hour mode is selectable.
• Capable of controlling the starting and stopping of the time-of-day clock.
• Provides a 30-second correction function to adjust time using a time signal.
• Includes a 1 Hz counter to count 128 to 1 Hz.
• Includes a BCD stopwatch counter with 1/100-second counting supported.
• Provides a theoretical regulation function to correct clock error due to frequency tolerance with no external parts
required.
Figure 10.1.1 shows the configuration of RTCA.
RTCA
f
OSC1
1-second
signal
RTC
count
control
circuit
Comparator
OSC1
oscillator
1/128
128
Hz
RTCTRM[6:0]
RTC
128HZ
64
Hz
RTC
64HZ
32
Hz
RTC
32HZ
16
Hz
RTC
16HZ
8
Hz
RTC
8HZ
4
Hz
RTC
4HZ
2
Hz
RTC
2HZ
1
Hz
RTC
1HZ
Clock generator
CPU core
RTCTRMBSY
RTCHLD
RTC24H
RTCADJ
Stopwatch
count
control
circuit
Interrupt
control
circuit
SWRST
SWRUN
SW1IE
SW10IE
SW100IE
ALARMIE
SW1IF
SW10IF
SW100IF
ALARMIF
RTCRST
RTCRUN
RTCWK[2:0]
RTCYH[3:0]
/RTCYL[3:0]
RTCMOH
/RTCMOL[3:0]
RTCDH[1:0]
/RTCDL[3:0]
RTCAP
RTCHH[1:0]
/RTCHL[3:0]
RTCMIH[2:0]
/RTCMIL[3:0]
RTCSH[2:0]
/RTCSL[3:0]
RTCAPA
RTCHHA[1:0]
/RTCHLA[3:0]
RTCMIHA[2:0]
/RTCMILA[3:0]
RTCSHA[2:0]
/RTCSLA[3:0]
RTCBSY
Day of
week
Year
Month
Day
A.M./
P.M.
Hour
Minute
Second
1 Hz counter
1/100
s
BCD
100[3:0]
1/10
s
BCD
10[3:0]
Stopwatch counter
Stopwatch counter interrupt
1 Hz counter interrupt
Alarm interrupt
Real-time clock counter interrupt
Real-time
clock
counter
Inter
nal data
bu
s
RTC1S
T1DAYIE
T1HURIE
T1MINIE
T1SECIE
T1_2SECIE
T1_4SECIE
T1_8SECIE
T1_32SECIE
T1DAYIF
T1HURIF
T1MINIF
T1SECIF
T1_2SECIF
T1_4SECIF
T1_8SECIF
T1_32SECIF
Figure 10.1.1 RTCA Configuration
10.2 Output Pin and External Connection
10.2.1 Output Pin
Table 10.2.1.1 shows the RTCA pin.
Table 10.2.1.1 RTCA Pin
Pin name
I/O
*
Initial status
*
Function
RTC1S
O
O (L)
1-second signal monitor output pin
*
Indicates the status when the pin is configured for RTCA.
If the port is shared with the RTCA output function and other functions, the RTCA function must be assigned to the
port. For more information, refer to the “I/O Ports” chapter.