ATMEGA8U2_14 Datasheet, PDF (247/310 Pages) ATMEL Corporation – 125 Powerful Instructions – Most Single Clock Cycle Execution

ATmega8U2/16U2/32U2
25.2 Fuse Bits
Table 25-2. Lock Bit Protection Modes⁽¹⁾⁽²⁾ (Continued)
Memory Lock Bits
Protection Type
BLB1 Mode BLB12 BLB11
1
1
1
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.
SPM is not allowed to write to the Boot Loader section, and
(E)LPM executing from the Application section is not allowed to
3
0
0
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.
(E)LPM executing from the Application section is not allowed to
4
0
1
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
The ATmega8U2/16U2/32U2 has three Fuse bytes. Table 25-3 - Table 25-5 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 25-3. Extended Fuse Byte
Fuse Low Byte
Bit No Description
–
7
–
–
6
–
–
5
–
–
4
–
HWBE
3
BODLEVEL2⁽¹⁾
2
BODLEVEL1⁽¹⁾
1
BODLEVEL0⁽¹⁾
0
Hardware Boot Enable
Brown-out Detector trigger level
Brown-out Detector trigger level
Brown-out Detector trigger level
Default Value : 0xF4
1
1
1
1
0 (programmed)
1 (unprogrammed)
0 (programmed)
0 (programmed)
Note: 1. See “System and Reset Characteristics” on page 267 for BODLEVEL Fuse decoding.
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