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OPTVERR bit seems to be erroneously set, why?

AVoel.1
Associate III

‎2022-03-17 01:53 PM

We are seeing a situation where the OPTVERR bit is unexpectedly set after power reset. We've checked and all the complement words in the Flash area for the option bytes are set correctly, so no corruption there. The description in the reference manual for why this bit gets set is confusing:

"Set by hardware when the options read may not be the one configured by the user. If option haven’t been properly loaded, OPTVERR is set again after each system reset."

To make the mystery even more intriguing, we are only seeing this on one of our two PCB board designs, even though both use identical STM32L452REY6 MCUs. The higher density board is exhibiting this problem, the lower density board is not. So it seems related to the HW environment, which on the surface makes very little sense. So two questions:

  1. Is there anything that should trigger the OPTVERR bit to be set other than the complement words not being set correctly in Flash?
  2. Could any HW environment cause this issue, maybe related to an Errata or brown out condition or ...?

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1 REPLY 1
waclawek.jan
Guru

‎2022-03-17 03:31 PM

> Could any HW environment cause this issue, maybe related to an Errata or brown out condition or ...?

I don't know, but let me reverse the question: are there differences in the HW environment between the boards? Perhaps a problematic/oscillating supply voltage rise? Ground pin voltage differences during powerup, problematic VDDA rise? Do you have BOR option bits set/setting them to a different value makes any difference?

JW

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