Datasheet

361
7593L–AVR–09/12
AT90USB64/128
Note: 1. The SPIEN Fuse is not accessible in serial programming mode.
2. See Table 29-8 on page 357 for details.
3. See “WDTCSR – Watchdog Timer Control Register” on page 65 for details.
4. Never ship a product with the OCDEN Fuse programmed regardless of the setting of Lock bits
and JTAGEN Fuse. A programmed OCDEN Fuse enables some parts of the clock system to
be running in all sleep modes. This may increase the power consumption.
Note: 1. The default value of SUT1..0 results in maximum start-up time for the default clock source
(258K CK + 4.1ms). See Table 9-1 on page 58 for details.
2. The default setting of CKSEL3..0 results in External Crystal Oscillator @ 8MHz. See Table 7-1
on page 41 for details.
3. The CKOUT Fuse allow the system clock to be output on PORTC7. See “Clock output buffer”
on page 47 for details.
4. See “System clock prescaler” on page 47 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.
30.2.1 Latching of fuses
The fuse v alues 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
Table 30-4. Fuse High Byte (AT90USB128: 0x99 - AT90USB64: 0x9B).
Fuse high byte Bit no. Description Default value
OCDEN
(4)
7 Enable OCD 1 (unprogrammed, OCD disabled)
JTAGEN 6 Enable JTAG 0 (programmed, JTAG enabled)
SPIEN
(1)
5
Enable Serial Program and Data
Downloading
0 (programmed, SPI prog. enabled)
WDTON
(3)
4 Watchdog Timer always on 1 (unprogrammed)
EESAVE 3
EEPROM memory is preserved
through the Chip Erase
1 (unprogrammed, EEPROM not
preserved)
BOOTSZ1 2
Select Boot Size (see Table 30-6
on page 363 for details)
0 (programmed)
(2)
BOOTSZ0 1
Select Boot Size (see Table 30-6
on page 363 for details)
0 (programmed)
(2)
(AT90USB128)
1 (unprogrammed)
(2)
(AT90USB64)
BOOTRST 0 Select Reset Vector 1 (unprogrammed)
Table 30-5. Fuse low byte (0x5E).
Fuse low byte Bit no. Description Default value
CKDIV8
(4)
7Divide clock by 8 0 (programmed)
CKOUT
(3)
6 Clock output 1 (unprogrammed)
SUT1 5 Select start-up time 0 (programmed)
(1)
SUT0 4 Select start-up time 1 (unprogrammed)
(1)
CKSEL3 3 Select Clock source 1 (unprogrammed)
(2)
CKSEL2 2 Select Clock source 1 (unprogrammed)
(2)
CKSEL1 1 Select Clock source 1 (unprogrammed)
(2)
CKSEL0 0 Select Clock source 0 (programmed)
(2)