Datasheet

283
4317K–AVR–03/2013
AT90PWM2/3/2B/3B
Notes: 1. See “Alternate Functions of Port C” on page 72 for description of RSTDISBL Fuse.
2. The SPIEN Fuse is not accessible in serial programming mode.
3. See “Watchdog Timer Configuration” on page 55 for details.
4. See Table 9-2 on page 48 for BODLEVEL Fuse decoding.
Note: 1. The default value of SUT1..0 results in maximum start-up time for the default clock source.
See Table 7-11 on page 38 for details.
2. The default setting of CKSEL3..0 results in internal RC Oscillator @ 8 MHz. See Table 7-11 on
page 38 for details.
3. The CKOUT Fuse allows the system clock to be output on PORTB0. See “Clock Output Buffer”
on page 38 for details.
4. See “System Clock Prescaler” on page 38 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.
25.3.1 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 25-5. Fuse High Byte
High Fuse Byte Bit No Description Default Value
RSTDISBL
(1)
7 External Reset Disable 1 (unprogrammed)
DWEN 6 debugWIRE Enable 1 (unprogrammed)
SPIEN
(2)
5
Enable Serial Program and
Data Downloading
0 (programmed, SPI
programming enabled)
WDTON
(3)
4 Watchdog Timer Always On 1 (unprogrammed)
EESAVE 3
EEPROM memory is
preserved through the Chip
Erase
1 (unprogrammed), EEPROM
not reserved
BODLEVEL2
(4)
2
Brown-out Detector trigger
level
1 (unprogrammed)
BODLEVEL1
(4)
1
Brown-out Detector trigger
level
1 (unprogrammed)
BODLEVEL0
(4)
0
Brown-out Detector trigger
level
1 (unprogrammed)
Table 25-6. Fuse Low Byte
Low Fuse Byte Bit No Description Default Value
CKDIV8
(4)
7 Divide clock by 8 0 (programmed)
CKOUT
(3)
6 Clock output 1 (unprogrammed)
SUT1 5 Select start-up time 1 (unprogrammed)
(1)
SUT0 4 Select start-up time 0 (programmed)
(1)
CKSEL3 3 Select Clock source 0 (programmed)
(2)
CKSEL2 2 Select Clock source 0 (programmed)
(2)
CKSEL1 1 Select Clock source 1 (unprogrammed)
(2)
CKSEL0 0 Select Clock source 0 (programmed)
(2)