14

7618C–AVR–07/08

Important note:

The bootloader performs a watchdog reset to generate the “hardware reset” that allows to exe-

cute the application section. After a watchdog reset occurs, the AVR watchdog is still running,

thus the application should take care to disable watchdog at program start-up (otherwise the

application that does not manage the hardware watchdog will run in an infinite reset loop).

4.11

Request From Host

4.12

Answer from Bootloader

No answer is returned by the device.

5.

Security

When the USB bootloader connection is initiated, the bootloader automatically enters a

read/write software security mode (independent of the product lock bits settings). This allows to

protect the on-chip flash content from read/write access over the USB interface. Thus the only

DFU command allowed after a USB bootloader connection is a “Full Chip Erase” command.

After this “Full Chip Erase” has been received and properly executed, all DFU commands are

allowed, and thus the on-chip flash can be reprogrammed and verified.

Command Identifier

data[0]

data[1]

data[2]

data[3]

data[4]

Description

Id_write_command

04h

03h

00h

Hardware reset

01h

address

LJMP address

IN

Jump O

SETUP

DFU_UPLOAD

OUT

ZLP

SETUP

DFU_UPLOAD

ption (3 or 5 Bytes)