STM32F091VBT6 abnormal behavior in first time programming and also USART

[Mohammad A]

I've bought a dozen of these chips. When I tried to programme them I found some abnormal behaviors.

The first one is sequence needed to run the chip for the first time. It is not possible to run anything on chip for the first power on. It's like if it is the first time chip is going to be used, it is required to turn on the MCU, programme something on it, turn it off, turn it on again so it run the code, otherwise it would not work at the first attempt. Of course there would be no problem at all after passing this steps.

The second one is USART6 and USART7 485DE pin on PF2 and PF3 don't function. PF2 is always on and PF3 is always off. They don't work for this alternative function. But of couse it is possible to control them in software and output mode.

I checked errata and did not find anything related to these problems. I also testified the reseller and it seems that chips are not counterfeit.

Besides these issues, chip works properly and I did not find any problem with it.

[Tesla DeLorean]

>>It is not possible to run anything on chip for the first power on.

I'm pretty sure the device runs from ROM and can be demonstrated to be doing so. That it doesn't run your code in FLASH, more likely than not, relates to the mapping of FLASH/ROM in the zero address space, and your ability to manage the vector table.

[Mohammad A]

I'd never experienced anything like that with any other MCUs from STM32 series.