Datasheet

148
ATtiny25/45/85 [DATASHEET]
2586Q–AVR–08/2013
20.2 Fuse Bytes
ATtiny25/45/85 has three fuse bytes, as described in Table 20-3, Table 20-4, and Table 20-5. Note that fuses are
read as logical zero, “0”, when programmed.
Notes: 1. Enables SPM instruction. See “Self-Programming the Flash” on page 141.
Notes: 1. Controls use of RESET
pin. See “Alternate Functions of Port B” on page 60.
2. After this fuse has been programmed device can be programmed via high-voltage serial mode, only.
3. Must be unprogrammed when lock bit security is required. See “Program And Data Memory Lock Bits” on page
147.
4. This fuse is not accessible in SPI programming mode.
5. See “WDTCR – Watchdog Timer Control Register” on page 45 for details.
6. See table “BODLEVEL Fuse Coding. TA = -40°C to +85°C” on page 166.
Table 20-3. 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
(1)
0 Self-programming enabled 1 (unprogrammed)
Table 20-4. Fuse High Byte
Fuse High Byte Bit No Description Default Value
RSTDISBL
(1) (2)
7 External reset disabled 1 (unprogrammed)
DWEN
(1) (2) (3)
6 DebugWIRE enabled 1 (unprogrammed)
SPIEN
(4)
5
Serial program and data download
enabled
0 (programmed)
(SPI prog. enabled)
WDTON
(5)
4 Watchdog timer always on 1 (unprogrammed)
EESAVE 3 EEPROM preserves chip erase
1 (unprogrammed)
(EEPROM not preserved)
BODLEVEL2
(6)
2 Brown-out Detector trigger level 1 (unprogrammed)
BODLEVEL1
(6)
1 Brown-out Detector trigger level 1 (unprogrammed)
BODLEVEL0
(6)
0 Brown-out Detector trigger level 1 (unprogrammed)