AN2430 Datasheet, PDF (15/24 Pages) STMicroelectronics – STR75x SystemMemory boot mode

AN2430
General description
1.4.9
Readout Temporary Unprotect command
Description:
This command allows the user to temporarily disable the readout protection for the entire
Flash.
When the bootloader receives the Readout Temporary Unprotect command, it transmits the
ACK byte.
After the transmission of the ACK byte, the bootloader erases all the Flash sectors then
temporarily disables the readout protection for the entire Flash.
If an error occurs during the erase operation the command is exited and the readout
protection remains enabled.
Finally, at the end of the command, the bootloader transmits the ACK byte if the readout
unprotection is completed successfully otherwise a NACK byte (0x3F) is returned to the
user and the command is exited.
Figure 9. Readout temporary unprotect command flowchart
Start ROU_TMP
Received byte
No
== 0x91?
Send ACK byte
Erase all the Flash sectors
Yes
Erase error?
Temporarily Disable the Readout
protection for the entire Flash
Yes
Protection error?
Send ACK byte
End of ROU_TMP
Send NACK byte
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