STM32F103 unique device identifier not found (response ffffffff)

[DStoi.1]

Hi,

I have an issue with STM32F103RCT6 MCUs. When trying to check the device unique identifier sometimes (about 5% of the chips I tested) the response I get from the chip is just:

ffffffff ffffffff ffffffff

instead of a "uuid-looking" 96-bit hexadecimal.

In what case can that be? Does that mean the chip is fake? I've heard that it could mean it's an engineering sample... But I couldn't find any further reference online.

I go looking at this address as per the reference manual: 0x1FFFF7E8 and look for the next 3 32-bit words:

openocd -f 'openocd_interface_target.cfg' -c 'init' -c 'stm32f1x.cpu mdw 0x1FFFF7E8 3' -c 'exit'

Any help or info appreciated. Thanks!

[TDK]

> Does that mean the chip is fake?

Did you pay $2 for a board from a no-name seller on eBay or buy a chip from a respected reseller like DigiKey?

Might not mean it's fake, but it probably means it wasn't intended for sale to an end user.

[DStoi.1]

Thanks for the answer.

I didn't buy the chips myself. A PCBA supplier did. So they should check their sources, but didn't buy direct from ST. I got a small amount of chips out of hundreds that are this way so I'm wondering...

[henry.dick]

not an openocd user myself. i would hook the chip to a stlink and read the right address to be sure.