Table 30-2. Lock Bit Protection Modes(1)(2) (Continued)
Memory Lock Bits
Protection Type
BLB1 Mode
BLB12
BLB11
No restrictions for SPM or (E)LPM accessing the Boot Loader
section.
1
2
1
1
1
0
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.
3
4
0
0
0
1
(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.
Notes: 1. Program the Fuse bits and Boot Lock bits before programming the LB1 and LB2.
2. “1” means unprogrammed, “0” means programmed
30.2 Fuse Bits
The ATmega640/1280/1281/2560/2561 has three Fuse bytes. Table 30-3 - Table 30-5 describe
briefly the functionality of all the fuses and how they are mapped into the Fuse bytes. Note that
the fuses are read as logical zero, “0”, if they are programmed.
Table 30-3. Extended Fuse Byte
Fuse Low Byte
Bit No
Description
Default Value
–
7
6
5
4
3
2
1
0
–
1
–
–
1
–
–
1
–
–
1
–
–
1
BODLEVEL2(Note:)
BODLEVEL1(Note:)
BODLEVEL0(Note:)
Brown-out Detector trigger level
Brown-out Detector trigger level
Brown-out Detector trigger level
1 (unprogrammed)
1 (unprogrammed)
1 (unprogrammed)
Note:
See “System and Reset Characteristics” on page 375 for BODLEVEL Fuse decoding.
338
ATmega640/1280/1281/2560/2561
2549L–AVR–08/07
ATMEL [ ATMEL ]
