Datasheet

164
7701F–AVR–10/12
Atmel ATtiny24/44/84 [Preliminary]
21.2 Fuse Bytes
The Atmel
®
ATtiny24/44/84 has three fuse bytes. Table 21-4 on page 164 to Table 21-5 on
page 165 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. See “Alternate Functions of Port B” on page 68 for description of RSTDISBL and DWEN
Fuses. When programming the RSTDISBL Fuse, High-voltage Serial programming has to
be used to change fuses to perform further programming
2. DWEN must be unprogrammed when Lock Bit security is required. See “Program And Data
Memory Lock Bits” on page 163.
3. The SPIEN Fuse is not accessible in SPI Programming mode.
4. See “WDT Configuration as a Function of the Fuse Settings of WDTON” on page 45 for
details.
5. See Table 22-5 on page 181 for BODLEVEL Fuse decoding.
Table 21-3. Fuse Extended Byte
Fuse High Byte Bit No Description Default Value
7 - 1 (unprogrammed)
6 - 1 (unprogrammed)
5 - 1 (unprogrammed)
4 - 1 (unprogrammed)
3 - 1 (unprogrammed)
2 - 1 (unprogrammed)
1 - 1 (unprogrammed)
SELFPRGEN 0 Self programming enable 1 (unprogrammed)
Table 21-4. Fuse High Byte
Fuse High Byte Bit No Description Default Value
RSTDISBL
(1)
7 External Reset disable 1 (unprogrammed)
DWEN
(2)
6 DebugWIRE Enable 1 (unprogrammed)
SPIEN
(3)
6
Enable Serial Program and Data
Downloading
0 (programmed, SPI
prog. enabled)
WDTON
(4)
4 Watchdog Timer always on 1 (unprogrammed)
EESAVE 3
EEPROM memory is preserved
through the Chip Erase
1 (unprogrammed,
EEPROM not
preserved)
BODLEVEL2
(5)
2 Brown-out Detector trigger level 1 (unprogrammed)
BODLEVEL1
(5)
1 Brown-out Detector trigger level 1 (unprogrammed)
BODLEVEL0
(5)
0 Brown-out Detector trigger level 1 (unprogrammed)