STM32 Flash getting erased

[thao pham]

Posted on July 10, 2018 at 18:10

We are using a STM32F407IGH6 in our design.  We may have an invalid configuration for this device.  Currently we are pulling PDR_ON low, but we are not driving the NRST pin externally.  This will be fixed in our next spin of the board.  It was a mistake when we did the board originally.  The issue I am having is that so far on two of the boards with this bug, we have noticed that the flash on the STM32 somehow got accidentally erased.  We will program the board and it will be working for a couple of days, then suddenly it would not work again.  Next, I would connect to the STM32 using STLink and the data read back would be all FFFF....   I have reworked 10 other boards with the external POR on the NRST pin and have not seen the issues on these board.  I want to fully understand what is causing the issue with the flash.  Can it be the POR and is it something else I'm overlooking?  Please provide feedback.

[thao pham]

Posted on July 10, 2018 at 18:44

This have only happened twice so far on two boards and I have not been successful in reproducing the error.

[AvaTar]

Posted on July 11, 2018 at 10:04

Does your firmware contain any IAP (Flash programming) code ?

Erasure of Flash does not just happen. The Flash technology requires voltages of 9...12V to erase/program Flash cells. These voltages are produced on-chip from the 3.3V Vcc with switched-capacitor converters. And those converters are only turned on when you unlock the flash for programming.