Preliminary
Real Time Clock
S3C2451
RISC MICROPROCESSOR
14-2
Preliminary product information describe products that are in development,
for which full characterization data and associated errata are not yet available.
Specifications and information herein are subject to change without notice.
14.3 Real Time Clock Operation Description
2
15
Clock
Divider
XTOrtc
XTIrtc
Control
Register
SEC
MIN
HOUR
DATE
DAY
MON
YEAR
Leap Year Generator
Alarm Generator
Reset
Register
1 Hz
ALMINT
RTCCON
RTCALM
RTCRST
Time Tick Generator
TICWKUP
TICNT
32KHz~1Hz
ALMWKUP
TICINT
Figure 14-1. Real Time Clock Block Diagram
14.3.1 Leap Year Generator
The leap year generator can determine the last date of each month out of 28, 29, 30, or 31, based on data from
BCDDAY, BCDMON, and BCDYEAR. This block considers leap year in deciding on the last date. An 8-bit
counter can only represent 2 BCD digits, therefore it cannot decide whether “00” year (the year with its last two
digits zeros) is a leap year or not. For example, it cannot discriminate between 1900 and 2000. To solve this
problem, the RTC block in S3C2451 has hard-wired logic to support the leap year in 2000. Note 1900 is not leap
year while 2000 is leap year in general Gregorian calendar. Therefore, two digits of 00 in S3C2451 denote 2000,
not 1900. So, RTC in S3C2451 supports from 1901 to 2099.