RV-8523 Datasheet, PDF (28/57 Pages) MICORO CRYSTAL SWITZERLAND – Real Time Clock

Micro Crystal
Real Time Clock / Calendar Module
RV-8523
During read/write operations, the time counting circuits (memory locations 03h through 09h) are blocked.
The blocking prevents:
• Faulty reading of the clock and calendar during a carry condition
• Incrementing the time registers during the read cycle
After the read/write access is completed, the time circuit is released again and any pending request to increment
the time counters that occurred during the read/write access is serviced. A maximum of one request can be stored;
therefore, all accesses must be completed within 1 second.
Access time for read/write operations:
Because of this method, it is very important to make a read or write access in one go, that is, setting or reading
seconds through years should be made in one single access. Failing to comply with this method could result in the
time becoming corrupted.
As an example, if the time (seconds through hours) is set in one access and then in a second access the date is
set, it is possible that the time will increment between the two accesses. A similar problem exists when reading. A
rollover may occur between reads thus giving the minutes from one moment and the hours from the next.
Recommended method for reading the time:
1. Send a START condition and the slave address for write (D0h)
2. Set the address pointer to 3 (Seconds) by sending 03h
3. Send a RE-START condition (STOP followed by START)
4. Send the slave address for read (D1h)
5. Read the seconds
6. Read the minutes
7. Read the hours
8. Read the days
9. Read the weekdays
10. Read the months
11. Read the years
12. Send a STOP condition
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