M28R400CT Datasheet, PDF (43/50 Pages) STMicroelectronics – 4 Mbit (256Kb x16, Boot Block) 1.8V Supply Flash Memory

Figure 20. Locking Operations Flowchart and Pseudo Code
M28R400CT, M28R400CB
Start
Write 60h
Write
01h, D0h or 2Fh
Write 90h
Read Block
Lock States
Locking
NO
change
confirmed?
YES
Write FFh
End
locking_operation_command (address, lock_operation) {
writeToFlash (any_address, 0x60) ; /*configuration setup*/
if (lock_operation==LOCK) /*to protect the block*/
writeToFlash (address, 0x01) ;
else if (lock_operation==UNLOCK) /*to unprotect the block*/
writeToFlash (address, 0xD0) ;
else if (lock_operation==LOCK-DOWN) /*to lock the block*/
writeToFlash (address, 0x2F) ;
writeToFlash (any_address, 0x90) ;
if (readFlash (address) ! = locking_state_expected)
error_handler () ;
/*Check the locking state (see Read Block Signature table )*/
writeToFlash (any_address, 0xFF) ; /*Reset to Read Array mode*/
}
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