208
ATmega8A [DATASHEET]
8159E–AVR–02/2013
Notes:
1. Program the Fuse Bits before programming the Lock Bits.
2. “1” means unprogrammed, “0” means programmed
25.2
Fuse Bits
The ATmega8A has two fuse bytes.
Table 25-3 and
Table 25-4 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.
Notes:
1. The SPIEN Fuse is not accessible in Serial Programming mode.
details.
4. When programming the RSTDISBL Fuse Parallel Programming has to be used to change fuses or perform further
programming.
11
1
No restrictions for SPM or LPM accessing the Boot Loader
section.
2
1
0
SPM is not allowed to write to the Boot Loader section.
30
0
SPM is not allowed to write to the Boot Loader section, and 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.
40
1
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 25-2.
Lock Bit Protection Modes
(2) (Continued)
Memory Lock Bits
Protection Type
Table 25-3.
Fuse High Byte
Fuse High
Byte
Bit No.
Description
Default Value
7
Select if PC6 is I/O pin or RESET pin
1 (unprogrammed, PC6 is
RESET-pin)
WDTON
6
WDT always on
1 (unprogrammed, WDT
enabled by WDTCR)
5
Enable Serial Program and Data
Downloading
0 (programmed, SPI prog.
enabled)
4
Oscillator options
1 (unprogrammed)
EESAVE
3
EEPROM memory is preserved through
the Chip Erase
1 (unprogrammed, EEPROM
not preserved)
BOOTSZ1
2
details)
BOOTSZ0
1
details)
BOOTRST
0
Select Reset Vector
1 (unprogrammed)