ATmega64A datasheet(297/392 Pages) ATMEL

297 / 392 page

297

8160C–AVR–07/09

ATmega64A

Note:

1. The SPIEN Fuse is not accessible in SPI Serial Programming mode.

2. The CKOPT Fuse functionality depends on the setting of the CKSEL bits. See

“Clock

Sources” on page 38 for details.

3. The default value of BOOTSZ1:0 results in maximum Boot Size. See Table 26-6 on page 292

4. If the JTAG interface is left unconnected, the JTAGEN fuse should if possible be disabled. This

to avoid static current at the TDO pin in the JTAG interface

Note:

1. The default value of SUT1:0 results in maximum start-up time. See Table 8-8 on page 42 for

details.

2. The default setting of CKSEL3:0 results in internal RC Oscillator @ 1 MHz. See Table 8-1 on

page 38 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.

27.2.1

Latching of Fuses

The fuse values 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 27-4.

Fuse High Byte

Bit no

Description

Default Value

OCDEN

Enable OCD

1 (unprogrammed, OCD

disabled)

JTAGEN(4)

Enable JTAG

0 (programmed, JTAG

enabled)

SPIEN(1)

Enable SPI Serial Program and Data

Downloading

0 (programmed, SPI prog.

enabled)

CKOPT(2)

Oscillator options

1 (unprogrammed)

EESAVE

EEPROM memory is preserved

through the Chip Erase

1 (unprogrammed, EEPROM

not preserved)

BOOTSZ1

Select Boot Size (see Table 26-6 for

details)

0 (programmed)(3)

BOOTSZ0

Select Boot Size (see Table 26-6 for

details)

0 (programmed)(3)

BOOTRST

Select Reset Vector

1 (unprogrammed)

Table 27-5.

Fuse Low Byte

Bit no

Description

Default Value

BODLEVEL

Brown out detector trigger level

1 (unprogrammed)

BODEN

Brown out detector enable

1 (unprogrammed, BOD disabled)

SUT1

Select start-up time

1 (unprogrammed)(1)

SUT0

Select start-up time

0 (programmed)(1)

CKSEL3

Select Clock source

0 (programmed)(2)

CKSEL2

Select Clock source

0 (programmed)(2)

CKSEL1

Select Clock source

0 (programmed)(2)

CKSEL0

Select Clock source

1 (unprogrammed)(2)

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