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We are using the STM32F051 series and have been experimenting with the flash memory protection. We have successfully protected some devices to level 1 i.e. set the RDP option byte to a value that neither 0xAA or 0xCC. However we now seem to have 'bricked' these devices! However my understanding is we should be able to go in and change this byte back to 0xAA which will erase the memory but at least we can then use the devices again. However we cannot gain access via the Keil ST-Link debugger. My question is - how do we recover these devices?
www.st.com/.../CD00264342.pdf "Readout Unprotect command"
You might also be able to use the ST-LINK utilities, but the serial port method is recommended.
When trying these things it's often advisable to add experimental code that reverses the state you're putting the part into, so you don't get in these one-way cul-de-sacs.