AT90USB646 datasheet(368/459 Pages) ATMEL

368 / 459 page

368

7593H–AVR–11/08

ATmega32U6/AT90USB64/128

Note:

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

2. See Table 28-8 on page 364 for details.

3. See “Watchdog Timer Control Register - WDTCSR” 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 8-1 on page 58 for details.

2. The default setting of CKSEL3..0 results in External Crystal Oscillator @ 8 MHz. See Table 6-

1 on page 40 for details.

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

on page 46 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.

Table 29-4.

Fuse High Byte (AT90USB128 : 0x99 - AT90USB64 : 0x9B)

Fuse High Byte

Bit No

Description

Default Value

OCDEN

(4)

Enable OCD

1 (unprogrammed, OCD disabled)

JTAGEN

Enable JTAG

0 (programmed, JTAG enabled)

SPIEN

(1)

Enable Serial Program and Data

Downloading

0 (programmed, SPI prog. enabled)

WDTON

(3)

Watchdog Timer always on

1 (unprogrammed)

EESAVE

EEPROM memory is preserved

through the Chip Erase

1 (unprogrammed, EEPROM not

preserved)

BOOTSZ1

Select Boot Size (see Table 29-6

for details)

0 (programmed)

(2)

BOOTSZ0

Select Boot Size (see Table 29-6

for details)

0 (programmed)

(2) (AT90USB128

and ATmega32U6)

1 (unprogrammed)

(2) (AT90USB64)

BOOTRST

Select Reset Vector

1 (unprogrammed)

Table 29-5.

Fuse Low Byte (0x5E)

Fuse Low Byte

Bit No

Description

Default Value

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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