DocID017068 Rev 4

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AN3156

DFU_DNLOAD request commands

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The Read Unprotect command is effectively executed only when a DFU_GETSTATUS

request is issued by the host. If the status returned by the device is not dfuDNBUSY, then an

error has occurred. After this operation, the device removes the Read Protection and,

consequently, both the internal Flash and the embedded RAM are fully erased.

Hence, just after executing this command, the device disconnects itself and executes a

system reset. In this case, the device is not able to respond to a second Get Status request.

And the host has to wait until the device is enumerated again.

A second DFU_GETSTATUS request may also be issued (if the device is still connected) to

check if the command has been correctly executed. If the device fails to execute the

command it returns an error status (depending on the error type).

Figure 10. Read Unprotect command: Device side

5.5

Leave DFU mode

It is possible to exit DFU mode (and bootloader) and jump to a loaded application (in the

internal Flash or in the embedded RAM) using the DFU download request.

The Host sends a DFU_DNLOAD request with 0 data length (no data stage after the

request) in order to inform the device that it will have to exit DFU mode. The device

acknowledges this request if the current state is dfuDNLOAD-IDLE or dfuIDLE.