Datasheet

336
2549O–AVR–05/12
ATmega640/1280/1281/2560/2561
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 through Table 30-5 on
page 337 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.
Note: 1. See “System and Reset Characteristics” on page 372 for BODLEVEL Fuse decoding.
BLB1 Mode BLB12 BLB11
111
No restrictions for SPM or (E)LPM accessing the Boot Loader
section.
2 1 0 SPM is not allowed to write to the Boot Loader section.
300
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.
401
(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.
Table 30-2. Lock Bit Protection Modes
(1)(2)
(Continued)
Memory Lock Bits Protection Type
Table 30-3. Extended Fuse Byte
Extended Fuse Byte Bit No Description Default Value
–7 – 1
–6 – 1
–5 – 1
–4 – 1
–3 – 1
BODLEVEL2
(1)
2 Brown-out Detector trigger level 1 (unprogrammed)
BODLEVEL1
(1)
1 Brown-out Detector trigger level 1 (unprogrammed)
BODLEVEL0
(1)
0 Brown-out Detector trigger level 1 (unprogrammed)