AN4221 Datasheet, PDF (44/51 Pages) STMicroelectronics – I2C protocol used in the STM32 bootloader

Bootloader command set
AN4221
Figure 31. No-Stretch Write unprotect command: device side
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1. WPUN = Write Unprotect.
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No-Stretch Readout protect command
The No-Stretch Readout Protect command is used to enable the Flash memory read
protection. When the bootloader receives the Readout Protect command, it transmits the
ACK byte to the host, enables the read protection for the Flash memory and returns Busy
state (0x76) while operation is ongoing.
At the end of the No-Stretch Readout Protect command, the bootloader transmits the ACK
byte and generates a system Reset to take the new configuration of the option byte into
account.
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DocID024055 Rev 2