ATmega128 datasheet(276/386 Pages) ATMEL

276 / 386 page

276

2467S–AVR–07/09

ATmega128

Note:

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

Note:

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

Entering the Boot

Loader Program

Entering the Boot Loader takes place by a jump or call from the application program. This may

be initiated by a trigger such as a command received via USART, or SPI interface. Alternatively,

the Boot Reset Fuse can be programmed so that the Reset Vector Reset 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 is pro-

grammed, 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

Table 108. Boot Lock Bit0 Protection Modes (Application Section)(1)

BLB0 mode

BLB02

BLB01

Protection

No restrictions for SPM or 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

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.

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 109. Boot Lock Bit1 Protection Modes (Boot Loader Section)

(1)

BLB1 mode

BLB12

BLB1

1Protection

No restrictions for SPM or 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 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.

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.

Table 110. Boot Reset Fuse

(1)

BOOTRST

Reset Address

Reset Vector = Application Reset (address $0000)

Reset Vector = Boot Loader Reset (see Table 112 on page 284)

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