Figure 4-1. Example of Firmware Download Zero Length DFU_DNLOAD Request
DFU_DNLOAD
SETUP
OUT
Prog_Start + (EP0 fifo length - 6) x 00h
X offset bytes + Firmware Packet 1
Firmware Packet 2
OUT
OUT
Firmware Packet n + DFU suffix
ZLP
OUT
IN
The Host sends a DFU_DNLOAD request with Zero Length Packet (ZLP) to indicate that it has
completed transferring the firmware image file. This is the final payload packet of a download
operation.
4.6.1.4
Answers from Bootloader
After each program request, the Host can request the device state and status by sending a
DFU_GETSTATUS message.
If the device status indicates an error, the host must send a DFU_CLRSTATUS request to the
device.
4.7
Reading the Flash or EEPROM Data
The flow described below allows the user to read data in the Flash memory or in the EEPROM
data memory. A blank check command on the Flash memory is possible with this flow.
This operation is performed in 2 steps:
• DFU_DNLOAD request with the read command (6 bytes)
• DFU_UPLOAD request which correspond to the previous command.
10
7618C–AVR–07/08
ATMEL [ ATMEL ]
