DOC7707 datasheet(229/307 Pages) ETC1

229 / 307 page

229

7707F–AVR–11/10

AT90USB82/162

Note:

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

Note:

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

23.5

Entering the Boot Loader Program

The bootloader can be executed with three different conditions:

23.5.1

Regular application conditions.

A jump or call from the application program. This may be initiated by a trigger such as a com-

mand received via USART, or SPI interface.

23.5.2

Boot Reset Fuse

The Boot Reset Fuse (BOOTRST) can be programmed so that the Reset Vector is pointing to

the Boot Flash start address after a reset. In this case, the Boot Loader is started after a reset.

After the application code is loaded, the program can start executing the application code. Note

that the fuses cannot be changed by the MCU itself. This means that once the Boot Reset Fuse

Table 23-2.

Boot Lock Bit0 Protection Modes (Application Section)(1)

BLB0 Mode

BLB02

BLB01

Protection

No restrictions for SPM or (E)LPM accessing the Application

section.

SPM is not allowed to write to the Application section.

SPM is not allowed to write to the Application section, and

(E)LPM executing from the Boot Loader section is not allowed to

read from the Application section. If Interrupt Vectors are placed

in the Boot Loader section, interrupts are disabled while

executing from the Application section.

(E)LPM executing from the Boot Loader section is not allowed to

read from the Application section. If Interrupt Vectors are placed

in the Boot Loader section, interrupts are disabled while

executing from the Application section.

Table 23-3.

Boot Lock Bit1 Protection Modes (Boot Loader Section)

(1)

BLB1 Mode

BLB12

BLB11

Protection

No restrictions for SPM or (E)LPM accessing the Boot Loader

section.

SPM is not allowed to write to the Boot Loader section.

SPM is not allowed to write to the Boot Loader section, and

(E)LPM executing from the Application section is not allowed to

read from the Boot Loader section. If Interrupt Vectors are

placed in the Application section, interrupts are disabled while

executing from the Boot Loader section.

(E)LPM executing from the Application section is not allowed to

read from the Boot Loader section. If Interrupt Vectors are

placed in the Application section, interrupts are disabled while

executing from the Boot Loader section.

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