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PCF2127 RTC RAM does not store data

Question asked by quex on Aug 9, 2019
Latest reply on Sep 29, 2019 by quex

I have a problem with one PCF2127 RTC IC.

The clock works, I can set and read the time via I2C.

 

The other feature I'm using is the backed-up RAM.

 

But when I write the registers and read them back, I get only zeros.

The PCF2127 responds, but the values are zero.

 

It looks like this:

Writing 5 bytes starting at address 0:

Reading the 5 bytes back:

 

On another unit (the same device type, identical MCU application) it behaves correctly:

Writing 5 bytes starting at address 0:

Reading the 5 bytes back:

 

I also tried writing 5 bytes @ address 64, but with the same result.

 

The schematics of the circuit:

It seems to me that the PCF2127 is defective.

Is there any procedure that could be used to test/identify the problem or restore the correct function?

Has this behavior been observed before?

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