topic Re: When PCF2129 information should be read/write? in Other NXP Products

When PCF2129 information should be read/write?

dominusdrr — Tue, 24 Sep 2019 20:06:40 GMT

Hi.

I have managed to send and receive information from the PCF2129 via SPI with a microcontroller.

Both writing and reading is done from address 0x03 (seconds) to address 0x09 (years).

But I have discovered that sometimes you write or receive erroneous data. For example, once the RTCC has been correctly matched, both time and date, such information obtains inconsistent data.

I read section 8.8.8 of the datasheets and it indicates that regions from address 0x03 to 0x09 are blocked for security.

Could that be the cause that sometimes I get incongruous data?

If the answer is yes, my question is: How can I know what is the right time to read the information from these regions of the RAM?

Any comments or suggestions are welcome.

Fabián

Re: When PCF2129 information should be read/write?

TomasVaverka — Wed, 25 Sep 2019 11:31:56 GMT

Hi Fabian,

Chapters 8.8.8 of the PCF2129 datasheet and 18 of the UM10301 provide additional information regarding reading to/writing from the time and date registers. Our recommendation is to read all time registers in one single read operation, using the auto-increment function. Is this what you are doing in your code?

Best regards,

Tomas

Re: When PCF2129 information should be read/write?

dominusdrr — Wed, 25 Sep 2019 13:02:39 GMT

That's exactly what I'm doing, I point to address 0x03 and by auto increment I read all the other bytes up to address 0x09

Re: When PCF2129 information should be read/write?

dominusdrr — Thu, 26 Sep 2019 02:00:57 GMT

Hi.

I had to solder wires to the SPI lines and the CE to connect a logic analyzer and determine what was happening.

It was a silly mistake, I was forgetting to put the CE terminal in logical 1 when the reading of all bytes was finished.

Re: When PCF2129 information should be read/write?

TomasVaverka — Thu, 26 Sep 2019 07:07:07 GMT

Hi Fabian,

OK, good to know what was behind this issue, I also always use a logic analyzer to make sure the format and timing of the SPI traffic meet datasheet recommendations.

Best regards,

Tomas