AT90USB64/128
Table 29-2. 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
0
0
(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.
4
0
1
Notes: 1. Program the Fuse bits and Boot Lock bits before programming the LB1 and LB2.
2. “1” means unprogrammed, “0” means programmed
29.2 Fuse Bits
The AT90USB64/128 has four Fuse bytes. Table 29-3 - Table 29-5 describe briefly the function-
ality 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 29-3. Extended Fuse Byte
Fuse Low Byte
Bit No
Description
Default Value
–
–
–
–
7
–
1
6
5
4
3
2
1
0
–
1
–
1
–
1
HWBE
Hardware Boot Enable
Brown-out Detector trigger level
Brown-out Detector trigger level
Brown-out Detector trigger level
0 (programmed)
1 (unprogrammed)
1 (unprogrammed)
1 (unprogrammed)
BODLEVEL2(1)
BODLEVEL1(1)
BODLEVEL0(1)
Note:
1. See Table 8-2 on page 61 for BODLEVEL Fuse decoding.
369
7593A–AVR–02/06
ATMEL [ ATMEL ]
