UM0116 Read/program the STR7 embedded Flash
A complete set of checks is done by the Flash controller after each write operation to verify that the operation completed successfully.
The FLASH_ER register provides dedicated flags for each error type that might arise during a write operation as well as a global flag triggered on any error.
The following errors may occur during write operation:
● Hardware errors:
– Program Error: this error reports a physical failure of a Flash cell that can no more be programmed. The word where this error occurred must be rejected.
– Erase Error: this error reports a physical failure of a Flash cell that can no more be programmed. The sector where this error occurred must be rejected.
● Software errors:
– 1 over 0 error: this error reports an attempt to program at ‘1’ a bit, whereas it was already programmed at ‘0’. The data should be masked with the current value, or the sector should erased before reprogramming this data.
– Sequence error: this error reports that an incorrect sequence has been executed to trigger the write operation. The code applying the sequence should be checked.
– Resume error: this error reports that a suspend write operation has not been correctly resumed. The full operation sequence has to be redone.
– Protection error: this error reports an attempt to write a sector which is write protected. If the sector effectively needs to be written, the sector should first be temporary unprotected, then the full operation sequence has to be reexecuted.
A failing write operation is normally flagged in the Flash Error Register (FLASH_ER).
Nevertheless, if during a write operation, the internal 1.8V Vdd supply drops below the internal Flash low voltage detector threshold or if a reset is triggered, the operation is suddenly interrupted and the Flash controller is reset to Read mode without updating the
FLASH_ER.
The sectors or words that were under modification while the write operation has been interrupted becomes undefined. The interrupted write operation must be repeated to recover these resources.
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