Testing margin level functionality on MC9S12ZVC

[TomoTom]

Hello,

I'm looking into user/field margin level functionality with DEVKIT-S12ZVC devboard. I came up with the code that changes margin level settings then reads EEPROM memory. All error bits in FSTAT register after change seem to be fine so I assume that margin is changed.

Now my question is: how can I test if the functionality works?

My idea was to change FDIV in FCLKDIV register to value outside of proper range for my BUSCLK frequency, since the documentation states that this could result in incomplete programming or erasure of memory. Then repeatedly erase, program and read memory with different margin settings with hope that I'll see the difference in read data.

Is this the right path or is there different way to test this?

Thanks for any help

[lama · Accepted solution]

Hi,

I tried to get anything but without success. Such study does not exist. 

Best regards,
Ladislav

[lama]

Hi,

There is no official method to inject margin level error.

The MCU determines the binary value of a flash cell by sensing the current through the cell. In normal operation, the MCU uses a measurement level that allows for the maximum discrimination between normally programmed or erased values. The charge values vary across a narrow distribution for a correctly programmed or erased cell. If the cell is marginally programmed or erased, the actual cell charge margin may be smaller than expected. This decreased margin could be further reduced by normal variations of the MCU caused by voltage or temperature fluctuations, or by the gradual change in charge on the cell over the course of many years.

Speculative approach can be programming cell with the low margin and increased frequency to reduce programming time. But there is no study of this approach as well as you use the device out of specifications and requirements.

Finally, after a lot of words, I am sorry I am not able to help because there is no solution even after discussion with colleagues.

Best regards,
Ladislav

[TomoTom]

Thanks for the quick reply.

Do you have any study on how the voltage or temperature fluctuations impact those margins or quality of erase and programming?