
222
4378C–AVR–09/08
AT90PWM1
Notes:
2. The SPIEN Fuse is not accessible in serial programming mode.
Note:
1. The default value of SUT1..0 results in maximum start-up time for the default clock source.
2. The default setting of CKSEL3..0 results in internal RC Oscillator @ 8 MHz. See
Table 7-10 on3. The CKOUT Fuse allows the system clock to be output on PORTB0. See
“Clock OutputThe 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.
22.3.1
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.
Table 77. Fuse High Byte
High Fuse Byte
Bit No
Description
Default Value
7
External Reset Disable
1 (unprogrammed)
DWEN
6
debugWIRE Enable
1 (unprogrammed)
5
Enable Serial Program and
Data Downloading
0 (programmed, SPI
programming enabled)
4
Watchdog Timer Always On
1 (unprogrammed)
EESAVE
3
EEPROM memory is
preserved through the Chip
Erase
1 (unprogrammed), EEPROM
not reserved
2
Brown-out Detector trigger
level
1 (unprogrammed)
1
Brown-out Detector trigger
level
1 (unprogrammed)
0
Brown-out Detector trigger
level
1 (unprogrammed)
Table 78. Fuse Low Byte
Low Fuse Byte
Bit No
Description
Default Value
7
Divide clock by 8
0 (programmed)
CKOUT
6
Clock output
1 (unprogrammed)
SUT1
5
Select start-up time
1 (unprogrammed)
SUT0
4
Select start-up time
0 (programmed)
CKSEL3
3
Select Clock source
CKSEL2
2
Select Clock source
CKSEL1
1
Select Clock source
1 (unprogrammed)
CKSEL0
0
Select Clock source