Microcontroller's reset pin behaviour when chip is blank

[yvesb]

HI all,

I noticed the reset pin gives a periodic pulse when the chip has never been flashed.

Is this a normal behaviour?

Regards,

Yves

[egoodii]

Certainly!  The 'invalid' PC/SP startup-values fetched from blank Flash memory quickly lead to 'nested hard faults', and the default power-on behavior for that condition ends in a hard reset, which starts the process all over again.

[yvesb]

thank you for your answer!

we have a problem, when the microcontroller has never been flashed, if the external watchdog timer is connected, we don't manage to flash it (using JTAG)