Datasheet

343
ATmega640/1280/1281/2560/2561
2549K–AVR–01/07
Notes: 1. Program the Fuse bits and Boot Lock bits before programming the LB1 and LB2.
2. “1” means unprogrammed, “0” means programmed
Fuse Bits The ATmega640/1280/1281/2560/2561 has three Fuse bytes. Table 151 - Table 153
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 Table 27 on page 60 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 150. Lock Bit Protection Modes
(1)(2)
(Continued)
Memory Lock Bits Protection Type
Table 151. Extended Fuse Byte
Fuse Low 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)