Hi Hans,

I use a cousin to your RTC, the PCF8563. A problem I had when dealing with its BCD registers was handling the unused/not implemented bits.

I was unable to assume they would be any given value, and had to mask them off so the remaining BCD value was valid.

Just something to think about. I don't know if your chip might have similar problem, and if that might be in any way related to your problem.

By the way, when I write a new time to the RTC, I write all the registers (including the control registers) as a block (I2C block write).

Dennis