AN3155 datasheet(33/37 Pages) STMICROELECTRONICS

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AN3155

Bootloader command set

3.12

Readout Unprotect command

The Readout Unprotect command is used to disable the Flash memory read protection.

When the bootloader receives the Readout Unprotect command, it transmits the ACK byte

to the host. After the transmission of the ACK byte, the bootloader erases all the Flash

memory sectors and it disables the read protection for the entire Flash memory. If the erase

operation is successful, the bootloader deactivates the RDP.

If the erase operation is unsuccessful, the bootloader transmits a NACK and the read

protection remains active.

At the end of the Readout Unprotect command, the bootloader transmits an ACK and

generates a system Reset to take into account the new configuration of the option byte.

Note:

For most STM32 products, the readout unprotect operation induce a mass erase of the flash

memory, so the Host has to wait sufficient time after the second ACK and before restarting

connection. To know how much time this operation takes, please refer to the mass erase

time in the product datasheet (when relevant).

Figure 24. Readout Unprotect command: host side

1. RDU_PRM = Readout Unprotect.

AN3155 Datasheet(PDF) 33 Page - STMicroelectronics