We are using PCF8583 with 89V51RD2 in many units. This works fine. But in rare cases we have found that the RTC stops responding to the I2C commands.
We have tried different recovery methods like
1. sending 9 times stop
2. sending start, 8 clocks and stop
3. sending start , 1 clock, and stop
4. stop, start, stop, start, address, check ack

NONE of the above bring out the RTC out of the hanged state.

Our experiance is if the battery power supply to the pcf8583 is turned off and ON, then it starts working again.

Please suggest if any known recovery procedure exist.

Also let me know, why the RTC would get stuck in this manner.

Thanks in advance
N B Patil