DOC7707 datasheet(245/307 Pages) ETC1

245 / 307 page

245

7707F–AVR–11/10

AT90USB82/162

Note:

1. The SPIEN Fuse is not accessible in serial programming mode.

2. The default value of BOOTSZ1..0 results in maximum Boot Size. See Table 23-8 on page 239

for details.

3. See “Watchdog Timer Control Register - WDTCSR” on page 56 for details.

4. Never ship a product with the DWEN Fuse programmed regardless of the setting of Lock bits

and RSTDSBL Fuse. A programmed DWEN 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.

See Table 9-1 on page 47 for details.

2. The default setting of CKSEL3..0 results in external Oscillator. See Table 6-1 on page 29 for

details.

3. The CKOUT Fuse allow the system clock to be output on PORTC7. See “Clock Output Buffer”

on page 34 for details.

4. See “System Clock Prescaler” on page 34 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.

Table 25-4.

Fuse High Byte

Bit No

Description

Default Value : 0xD9

DWEN(4)

Enable debugWIRE (and disable

Reset capability

1 (unprogrammed, debugWIRE

disabled)

RSTDSBL

Disable Reset (pin can be used as

general purpose I/O)

1 (unprogrammed, Reset

enabled)

SPIEN(1)

Enable Serial Program and Data

Downloading

0 (programmed, SPI prog.

enabled)

WDTON(3)

Watchdog Timer always ON

1 (unprogrammed)(3)

EESAVE

EEPROM memory is preserved

through the Chip Erase

1 (unprogrammed, EEPROM

not preserved)

BOOTSZ1

Select Boot Size (see Table 25-6 for

details)

0 (programmed)(2)

BOOTSZ0

Select Boot Size (see Table 25-6 for

details)

0 (programmed)(2)

BOOTRST

Select Bootloader Address as Reset

Vector

1 (unprogrammed, Reset vector

@0x0000)

Table 25-5.

Fuse Low Byte

Bit No

Description

Default Value : 0x5E

CKDIV8(4)

Divide clock by 8

0 (programmed)

CKOUT(3)

Clock output

1 (unprogrammed)

SUT1

Select start-up time

0 (programmed)(1)

SUT0

Select start-up time

1 (unprogrammed)(1)

CKSEL3

Select Clock source

1 (unprogrammed)(2)

CKSEL2

Select Clock source

1 (unprogrammed)(2)

CKSEL1

Select Clock source

1 (unprogrammed)(2)

CKSEL0

Select Clock source

0 (programmed)(2)

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