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Non Volatile RAM (F-RAM & NVSRAM)

Anonymous
Not applicable

I was checking out a FM25VN10 FRAM (an SPI device) using a Raspberry Pi, trying to put together some code for a project which will need to access it in a design. I satisfied myself that I could read and write FRAM memory locations, as well as read out the serial number and device ID.

   

A few days later I ran the same code and found that all the serial number and device ID bytes read out as zero (the device ID 0x7f continuation bytes remained for some reason). Importantly, I saw that my previously-written data was still there. I changed out the chip and ran the same code again on the new chip, and read out a normal serial number and correct device ID.

   

Can there be an undocumented SPI command which might cause the zeroing of these fields? If so, is there some way to lock-out that functionality?

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1 Solution
GirijaC_46
Moderator
Moderator

Hi,

   

The corruption may happen due to power ramp specifications violation of the device provided in the datasheet. This might be configuration register corruption which happens during the power up which is causing this failure. Please re-validate your power ramp transitions to avoid same failure on the other chip.

   

Regards,

   

Giirja

View solution in original post

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3 Replies
Anonymous
Not applicable

Hi,

   

We do not have any undocumented SPI command which will cause the zeroing of Device ID and serial number. The Device ID bytes are Read only Bytes.

   

Do you see the same behavior with the new device also. On how many devices did you observe this issue.

   

 

   

Thanks,

   

Krishna.

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Anonymous
Not applicable

Sadly, my sample size was 2. 🙂 I haven't done much with the second sample chip so far, but I will continue to revisit it in the coming weeks.

   

I still can't rule out the possibility that the first sample chip was stressed inadvertently through ESD or incorrect power application, so I'm not ready to indict the chip design based on one failure.

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GirijaC_46
Moderator
Moderator

Hi,

   

The corruption may happen due to power ramp specifications violation of the device provided in the datasheet. This might be configuration register corruption which happens during the power up which is causing this failure. Please re-validate your power ramp transitions to avoid same failure on the other chip.

   

Regards,

   

Giirja

View solution in original post

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