Datasheet

360
7593L–AVR–09/12
AT90USB64/128
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 Atmel AT90USB64/128 has four Fuse bytes. Table 30-3 - Table 30-5 on page 361 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 9-2 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 30-2. Lock bit protection modes
(1)(2)
. (Continued)
Memory lock bits Protection type
Table 30-3. Extended Fuse Byte (0xF3).
Fuse low byte Bit no. Description Default value
–7– 1
–6– 1
–5– 1
–4– 1
HWBE 3 Hardware Boot Enable 0 (programmed)
BODLEVEL2
(1)
2Brown-out Detector trigger level 0 (programmed)
BODLEVEL1
(1)
1Brown-out Detector trigger level 1 (unprogrammed)
BODLEVEL0
(1)
0Brown-out Detector trigger level 1 (unprogrammed)