8

7618C–AVR–07/08

4.5.3

Device State

The state reported is the current state of the device up to transmission of the response. The val-

ues specified in the bState field are identical to those reported in DFU_GETSTATUS.

4.5.4

DFU_ABORT request

The DFU_ABORT request forces the device to exit from any other state and return to the

DFU_IDLE state. The device sets the OK status on receipt of this request. For more information,

see the corresponding state transition summary.

4.6

Programming the Flash or EEPROM Data

The firmware image is downloaded via control-write transfers initiated by the DFU_DNLOAD

class-specific request. The host sends between bMaxPacketSize0 and wTransferSize bytes to

the device in a control-write transfer. Following each downloaded block, the host solicits the

device status with the DFU_GETSTATUS request.

As described in the USB DFU Specification, "Firmware images for specific devices are, by defi-

nition, vendor specific. It is therefore required that target addresses, record sizes, and all other

information relative to supporting an upgrade are encapsulated within the firmware image file. It

is the responsibility of the device manufacturer and the firmware developer to ensure that their

devices can process these encapsulated data. With the exception of the DFU file suffix, the con-

tent of the firmware image file is irrelevant to the host."

Firmware image:

• 32 bytes: Command

• X bytes: X is the number of byte (00h) added before the first significant byte of the firmware.

The X number is calculated to align the beginning of the firmware with the flash page. X =

start_address [32]. For example, if the start address is 00AFh (175d), X = 175 [32] = 15.

• The firmware

• The DFU Suffix on 16 Bytes.

Table 4-7.

DFU File Suffix

bmRequestType

bRequest

wValue

wIndex

wLength

Data

1010 0001b

DFU_GETSTATE (5)

Zero

Interface (4)

1

State

bmRequestType

bRequest

wValue

wIndex

wLength

Data

1010 0001b

DFU_ABORT (6)

Zero

Interface (4)

0

None

Offset

Field

Size

Value

Description

-0

dwCRC

4

Number

The CRC of the entire file, excluding dwCRC

-4

bLength

1

16

The length of this DFU suffix including dwCRC

-5

ucDfuSignature

3

5 : 44h

6 : 46h

7 : 55h

The unique DFU signature field

-8

bcdDFU

2

BCD

0100h

DFU specification number