257
Atmel ATmega16/32/64/M1/C1 [DATASHEET]
7647K–AVR–12/13
25.3
PSC Output Behavior during Reset
For external component safety reason, the state of PSC outputs during reset can be programmed by fuses PSCRB, PSCARV
If PSCRB fuse equals 1 (unprogrammed), all PSC outputs keep a standard port behavior. If PSC0RB fuse equals 0
(programmed), all PSC outputs are forced at reset to low level or high level according to PSCARV and PSCBRV fuse bits. In
PSCARV (PSCOUTnA reset value) gives the state low or high which will be forced on PSCOUT0A, PSCOUT1A and
PSCOUT2A outputs when PSCRB is programmed. If PSCARV fuse equals 0 (programmed), the PSCOUT0A, PSCOUT1A and
PSCOUT2A outputs will be forced to high state. If PSCRV fuse equals 1 (unprogrammed), the PSCOUT0A, PSCOUT1A and
PSCOUT2A outputs will be forced to low state.
PSCBRV (PSCOUTnB Reset Value) gives the state low or high which will be forced on PSCOUT0B, PSCOUT1B and
PSCOUT2B outputs when PSCRB is programmed. If PSCBRV fuse equals 0 (programmed), the PSCOUT0B, PSCOUT1B and
PSCOUT2B outputs will be forced to high state. If PSCRV fuse equals 1 (unprogrammed), the PSCOUT0B, PSCOUT1B and
PSCOUT2B outputs will be forced to low state.
Note:
1.
2.
The SPIEN fuse is not accessible in serial programming mode.
3.
4.
Table 25-5. PSC Output Behavior during and after Reset until POC Register is Written
PSCRB
PSCARV
PSCBRV
PSCOUTnA
PSCOUTnB
Unprogrammed
X
Normal port
Programmed
Unprogrammed
Forced low
Programmed
Unprogrammed
Programmed
Forced low
Forced high
Programmed
Unprogrammed
Forced high
Forced low
Programmed
Forced high
BODLEVEL2(1)
2
Brown-out detector
trigger level
1 (unprogrammed)
BODLEVEL1(1)
1
Brown-out detector
trigger level
1 (unprogrammed)
BODLEVEL0(1)
0
Brown-out detector
trigger level
1 (unprogrammed)
Table 25-6.
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
BOOTSZ1
2
Select boot size
0 (programmed)(4)
BOOTSZ0
1
Select boot size
0 (programmed)(4)
BOOTRST
0
Select reset vector
1 (unprogrammed)