25.2 Fuse Bits
The AT90PWM2/2B/3/3B has three Fuse bytes. Table 25-4 - Table 25-6 describe briefly 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.
Table 25-4. Extended Fuse Byte
Extended Fuse Byte
PSC2RB
PSC1RB
PSC0RB
PSCRV
Bit No
Description
Default Value
7
6
5
4
3
PSC2 Reset Behaviour
PSC1 Reset Behaviour
PSC0 Reset Behaviour
PSCOUT Reset Value
–
1
1
1
1
1
–
Select Boot Size
(see Table 113 for details)
BOOTSZ1
2
0 (programmed)(1)
Select Boot Size
(see Table 113 for details)
BOOTSZ0
BOOTRST
1
0
0 (programmed)(1)
1 (unprogrammed)
Select Reset Vector
Note:
1. The default value of BOOTSZ1..0 results in maximum Boot Size. See Table 25-7 on page 283
for details.
25.3 PSC Output Behaviour During Reset
For external component safety reason, the state of PSC outputs during Reset can be pro-
grammed by fuses PSCRV, PSC0RB, PSC1RB & PSC2RB.
These fuses are located in the Extended Fuse Byte ( see Table 25-4)
PSCRV gives the state low or high which will be forced on PSC outputs selected by PSC0RB,
PSC1RB & PSC2RB fuses.
If PSCRV fuse equals 0 (programmed), the selected PSC outputs will be forced to low state. If
PSCRV fuse equals 1 (unprogrammed), the selected PSC outputs will be forced to high state.
If PSC0RB fuse equals 1 (unprogrammed), PSCOUT00 & PSCOUT01 keep a standard port
behaviour. If PSC0RB fuse equals 0 (programmed), PSCOUT00 & PSCOUT01 are forced at
reset to low level or high level according to PSCRV fuse bit. In this second case, PSCOUT00 &
PSCOUT01 keep the forced state until PSOC0 register is written..
If PSC1RB fuse equals 1 (unprogrammed), PSCOUT10 & PSCOUT11 keep a standard port
behaviour. If PSC1RB fuse equals 0 (programmed), PSCOUT10 & PSCOUT11 are forced at
reset to low level or high level according to PSCRV fuse bit. In this second case, PSCOUT10 &
PSCOUT11 keep the forced state until PSOC1 register is written.
If PSC2RB fuse equals 1 (unprogrammed), PSCOUT20, PSCOUT21, PSCOUT22 &
PSCOUT23 keep a standard port behaviour. If PSC1RB fuse equals 0 (programmed),
PSCOUT20, PSCOUT21, PSCOUT22 & PSCOUT23 are forced at reset to low level or high
level according to PSCRV fuse bit. In this second case, PSCOUT20, PSCOUT21, PSCOUT22 &
PSCOUT23 keep the forced state until PSOC2 register is written.
280
AT90PWM2/3/2B/3B
4317J–AVR–08/10
ATMEL [ ATMEL ]
