Datasheet

159
8183F–AVR–06/12
ATtiny24A/44A/84A
19.2 Fuse Bytes
The ATtiny24A/44A/84A have three fuse bytes. Table 19-3, Table 19-4 and Table 19-5 briefly
describe 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. Enables SPM instruction. See “Self-Programming the Flash” on page 152.
Notes: 1. See “Alternate Functions of Port B” on page 64 for description of RSTDISBL and DWEN
Fuses. After programming the RSTDISBL fuse, high-voltage serial programming must be used
to change fuses and allow further programming.
2. DWEN must be unprogrammed when Lock Bit security is required. See “Program And Data
Memory Lock Bits” on page 158.
3. The SPIEN Fuse is not accessible in SPI programming mode.
4. Programming this fues will disable the Watchdog Timer Interrupt. See “WDT Configuration as
a Function of the Fuse Settings of WDTON” on page 42 for details.
5. See Table 20-6 on page 176 for BODLEVEL Fuse decoding.
Table 19-3. Fuse Extended Byte
Fuse Extended 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
(1)
0 Self-Programming Enable 1 (unprogrammed)
Table 19-4. 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)