STM32F100 writing to FLASH->KEYR causes hard fault

[julian239955_stm1_st]

Posted on April 19, 2017 at 17:52

I'm using the standard ST libraries and calling FLASH_Unlock

on   FLASH->KEYR = FLASH_KEY1;

I get a hard fault.

Using STlink and examining the option bytes there seems to be no protection active only WDG_SW, nRST_STOP and nBFB2.

Is there some form of memory protection that I should be disabling?