2

7618C–AVR–07/08

2.

Bootloader Environment

The bootloader is located in the boot section of the on-chip Flash memory, it manages the USB

communication protocol and performs read/write operations to the on-chip memories

(Flash/EEPROM).

The USB bootloader is loaded in the “Bootloader Flash Section” of the on-chip Flash memory.

The size of the bootloader flash section must be larger than the bootloader size.USB products

are factory configured with the default on-chip USB bootloader and the required bootsection

configuration.

Table 2-1.

USB Bootloader Parameters

Figure 2-1.

Physical Environment

3.

Bootloader Activation

As specified in the AT90USB datasheet, the bootloader can be activated by one of the following

conditions:

• Regular application execution: A jump or call from the user application program. This may

be initiated by a trigger such as a command received via USB, USART or SPI and decoded

by the application.

Product

Flash Bootsection Size

Configuration

VID / PID

Bootloader Start Address

(word address)

AT90USB1287

4 KWord

0x03EB / 0x2FFB

0xf000

AT90USB1286

AT90USB647

2 KWord

0x03EB / 0x2FF9

0x7800

AT90USB646

AT90USB162

0x03EB / 0x2FFA

0x1800

AT90USB82

0x03EB / 0x2FF7

0x0800

ATmega32U4

0x03EB / 0x2FF4

0x3800

ATmega16U4

0x03EB / 0x2FF3

0x0800

USB Bootloader

in Boot section

Flash

Application section

Read/Write

USB

Interface

EEPROM Data

Read/Write

DFU Class