RV-8564 Datasheet, PDF (19/40 Pages) MICORO CRYSTAL SWITZERLAND – I2C-Bus Interface Real Time Clock

Micro Crystal
Real Time Clock / Calendar Module
RV-8564
During read / write operations, the time counting circuits (memory locations 02h through 08h) are blocked, in order
to prevent the following:
• Faulty writing or reading of the clock and calendar during a carry condition
• Incrementing the time registers during the read cycle
After this 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 access is serviced. A maximum of 1 request can be stored;
therefore, all accesses must be completed within 1 second.
As a consequence of this method, it is very important to make a read or write access in one go. This means, 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 may be incremented between the two accesses. A similar problem exists when
reading. A roll over 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 (A2h)
2. Set the address pointer to 2 (seconds) by sending 02h
3. Send a RE-START condition or STOP followed by START
4. Send the slave address for read (A3h)
5. Read the seconds
6. Read the minutes
7. Read the hours
8. Read the days
9. Read the weekdays
10. Read the century and months
11. Read the years
12. Send a STOP condition
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