136
7598H–AVR–07/09
ATtiny25/45/85
Notes:
1. See
“Alternate Functions of Port B” on page 54
for description of RSTDISBL and DWEN
Fuses.
2. DWEN must be unprogrammed when Lock Bit security is required.
Memory Lock Bits” on page 134.
3. The SPIEN Fuse is not accessible in SPI Programming mode.
4. See
“Watchdog Timer Control Register – WDTCR” on page 42
for details.
5. See
for BODLEVEL Fuse decoding.
6. When programming the RSTDISBL Fuse, High-voltage Serial programming has to be used to
change fuses to perform further programming.
Notes:
1. See
“System Clock Prescaler” on page 29
for details.
2. The CKOUT Fuse allows the system clock to be output on PORTB4. See “Clock Output Buffer”
on page 30 for details.
3. The default value of SUT1..0 results in maximum start-up time for the default clock source.
for details.
4. The default setting of CKSEL1..0 results in internal RC Oscillator @ 8.0 MHz. See
for details.
The status of the Fuse bits is not affected by Chip Erase. Note that the Fuse bits are locked if
Lock bit1 (LB1) is programmed. Program the Fuse bits before programming the Lock bits.
21.2.1
Latching of Fuses
The fuse values are latched when the device enters programming mode and changes of the
fuse values will have no effect until the part leaves Programming mode. This does not apply to
the EESAVE Fuse which will take effect once it is programmed. The fuses are also latched on
Power-up in Normal mode.
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)
Table 21-5.
Fuse Low Byte
Fuse Low Byte
Bit No
Description
Default Value
CKDIV8
(1)
7
Divide clock by 8
0 (unprogrammed)
CKOUT
(2)
6
Clock Output Enable
1 (unprogrammed)
SUT1
5
Select start-up time
1 (unprogrammed)
SUT0
4
Select start-up time
0 (programmed)
CKSEL3
3
Select Clock source
0 (programmed)
CKSEL2
2
Select Clock source
0 (programmed)
CKSEL1
1
Select Clock source
1 (unprogrammed)
CKSEL0
0
Select Clock source
0 (programmed)
Table 21-4.
Fuse High Byte
Fuse High Byte
Bit No
Description
Default Value
