• When executing a flash erase verify (0x05) command sequence to a flash block different from the block where the backdoor keys are written to, both blocks will be erase verified. Any programmed location in either block will terminate the operation preventing the FSTAT.BLANK flag from setting.

• When executing a flash data compress (0x06) command sequence to a flash block different from the block where the backdoor keys are written to, a given number of words from both blocks will be compressed, this number will be equal to the value written at last key�s address. The signature from the block containing the backdoor keys will affect the signature returned in the FDATA register.

• When executing a flash program (0x20) command sequence to a flash block different from the block where the backdoor keys are written to, both blocks will be programmed at the same relative address with the unselected block being programmed to a data value equal to the last key written. Setting protection at the location in the block where the backdoor keys are written will not prevent the flash command from executing.

• When executing a flash sector erase (0x40) command sequence to a flash block different from the block where the backdoor keys are written to, both blocks will receive the erase at the sector address provided in the flash sector erase command sequence. Setting protection in the location where the backdoor keys are written to will not prevent the flash command from executing.

• When executing a flash mass erase (0x41) command sequence to a flash block different from the block where the backdoor keys are written to, both blocks will be erased. Setting protection in the block where the backdoor keys are written to will not prevent the flash command from executing.

• The flash sector erase abort (0x47) command is not impacted as all active sector erase operations will be terminated if successfully aborted.

When backdoor keys are written to the flash, the block selected by the keys remains selected and the last key is stored in the associated data register. If a flash command is launched on a different block before writing 1 to either PVIOL or ACCERR bits, the command will also execute on the block where the last key was written to. Also, commands that use the data field, such as data compress and program commands, will be impacted by the data from the last key written as follows:

• Data compress command will compress a given number of words from both blocks; this number will be equal to the last key written, and the signature from the block containing the backdoor keys will affect the signature returned in the FDATA register.


• Program command will program both blocks at the same relative address with the unselected block being programmed with a data value equal to the last key written.

Write 0x30 to FSTAT register (ACCERR = 1, PVIOL = 1) prior to executing any flash command sequence when backdoor keys have been written. This step can be done in conjunction with or instead of checking the FSTAT register as shown in the flash command sequence flow in the reference manual.