DOC7707 datasheet(230/307 Pages) ETC1

230 / 307 page

230

7707F–AVR–11/10

AT90USB82/162

is programmed, the Reset Vector will always point to the Boot Loader Reset and the fuse can

only be changed through the serial or parallel programming interface.

Note:

1. “1” means unprogrammed, “0” means programmed

23.5.3

External Hardware conditions

The Hardware Boot Enable Fuse (HWBE) can be programmed (See Table 23-5) so that upon

special hardware conditions under reset, the bootloader execution is forced after reset.

Note:

1. “1” means unprogrammed, “0” means programmed

When the HWBE fuse is enable the PD7/HWB pin is configured as input during reset and sam-

pled during reset rising edge. When PD7/HWB pin is ‘0’ during reset rising edge, the reset vector

will be set as the Boot Loader Reset address and the Boot Loader will be executed (See Figures

23-3).

Table 23-4.

Boot Reset Fuse(1)

BOOTRST

Reset Address

Reset Vector = Application Reset (address 0x0000)

Reset Vector = Boot Loader Reset (see Table 23-8 on page 239)

Table 23-5.

Hardware Boot Enable Fuse(1)

HWBE

Reset Address

1PD7/HWB pin can not be used to force Boot Loader execution after reset

0PD7/HWB pin is used during reset to force bootloader execution after reset

DOC7707 Datasheet(PDF) 230 Page - List of Unclassifed Manufacturers