Fuse Bytes - Atmel ATtiny25 Manual

21.2

Fuse Bytes

7598H–AVR–07/09
Table 21-2. Lock Bit Protection Modes
Memory Lock Bits
LB Mode LB2
1 1
2 1
3 0
Notes: 1. Program the Fuse bits before programming the LB1 and LB2.
2. "1" means unprogrammed, "0" means programmed
The ATtiny25/45/85 has three Fuse bytes.
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 21-3. Fuse Extended Byte
Fuse High Byte Bit No
7
6
5
4
3
2
1
SELFPRGEN 0
Table 21-4. Fuse High Byte
Fuse High Byte Bit No
(1)
RSTDISBL 7
(2)
DWEN 6
(3)
SPIEN 5
(4)
WDTON 4
EESAVE 3
(1)(2)
Protection Type
LB1
1 No memory lock features enabled.
Further programming of the Flash and EEPROM is disabled in
High-voltage and Serial Programming mode. The Fuse bits are
0
locked in both Serial and High-voltage Programming mode.
debugWire is disabled.
Further programming and verification of the Flash and
EEPROM is disabled in High-voltage and Serial Programming
0
mode. The Fuse bits are locked in both Serial and High-voltage
Programming mode.
Table 21-4,
Description
-
-
-
-
-
-
-
Self-Programming Enable
Description
External Reset disable
DebugWIRE Enable
Enable Serial Program and Data
Downloading
Watchdog Timer always on
EEPROM memory is preserved
through the Chip Erase
ATtiny25/45/85
(1)
debugWire is disabled.
Table 21-5 and Table61 describe briefly
Default Value
1 (unprogrammed)
1 (unprogrammed)
1 (unprogrammed)
1 (unprogrammed)
1 (unprogrammed)
1 (unprogrammed)
1 (unprogrammed)
1 (unprogrammed)
Default Value
1 (unprogrammed)
1 (unprogrammed)
0 (programmed, SPI prog.
enabled)
1 (unprogrammed)
1 (unprogrammed, EEPROM
not preserved)
(1)
135