ATMEGA640 datasheet(325/436 Pages) MICROCHIP

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ATmega640/V-1280/V-1281/V-2560/V-2561/V [DATASHEET]

DS40002211A

30. Memory Programming

30.1 Program And Data Memory Lock Bits

The ATmega640/1280/1281/2560/2561 provides six Lock bits which can be left unprogrammed (“1”) or can be pro-

grammed (“0”) to obtain the additional features listed in Table 30-2. The Lock bits can only be erased to “1” with the

Chip Erase command.

Note:

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

Table 30-1.

Lock Bit Byte(1)

Lock Bit Byte

Bit No

Description

Default Value

–

1 (unprogrammed)

–

1 (unprogrammed)

BLB12

Boot Lock bit

1 (unprogrammed)

BLB11

Boot Lock bit

1 (unprogrammed)

BLB02

Boot Lock bit

1 (unprogrammed)

BLB01

Boot Lock bit

1 (unprogrammed)

LB2

Lock bit

1 (unprogrammed)

LB1

Lock bit

1 (unprogrammed)

Table 30-2.

Lock Bit Protection Modes(1)(2)

Memory Lock Bits

Protection Type

LB Mode

LB2

LB1

No memory lock features enabled.

Further programming of the Flash and EEPROM is disabled in Parallel and Serial

Programming mode. The Fuse bits are locked in both Serial and Parallel

Programming mode.(1)

Further programming and verification of the Flash and EEPROM is disabled in

Parallel and Serial Programming mode. The Boot Lock bits and Fuse bits are locked

in both Serial and Parallel Programming mode.(1)

BLB0 Mode

BLB02

BLB01

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.

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