ATmega128 datasheet(297/386 Pages) ATMEL

297 / 386 page

297

2467S–AVR–07/09

ATmega128

Programming the

Fuse High Bits

The algorithm for programming the Fuse High bits is as follows (refer to “Programming the

Flash” on page 293 for details on Command and Data loading):

A: Load Command “0100 0000”.

C: Load Data Low Byte. Bit n = “0” programs and bit n = “1” erases the Fuse bit.

Set BS1 to “1” and BS2 to “0”. This selects high data byte.

Give WR a negative pulse and wait for RDY/BSY to go high.

Set BS1 to “0”. This selects low data byte.

Programming the

Extended Fuse Bits

The algorithm for programming the Extended Fuse bits is as follows (refer to “Programming the

Flash” on page 293 for details on Command and Data loading):

A: Load Command “0100 0000”.

C: Load Data Low Byte. Bit n = “0” programs and bit n = “1” erases the Fuse bit.

Set BS2 to “1” and BS1 to “0”. This selects extended data byte.

Give WR a negative pulse and wait for RDY/BSY to go high.

Set BS2 to “0”. This selects low data byte.

Figure 139. Programming the Fuses

Programming the Lock

Bits

The algorithm for programming the Lock bits is as follows (refer to “Programming the Flash” on

page 293 for details on Command and Data loading):

A: Load Command “0010 0000”.

C: Load Data Low Byte. Bit n = “0” programs the Lock bit.

Give WR a negative pulse and wait for RDY/BSY to go high.

The Lock bits can only be cleared by executing Chip Erase.

Reading the Fuse and

Lock Bits

The algorithm for reading the Fuse and Lock bits is as follows (refer to “Programming the Flash”

on page 293 for details on Command loading):

A: Load Command “0000 0100”.

Set OE to “0”, BS2 to “0”, and BS1 to “0”. The status of the Fuse Low bits can now be

read at DATA (“0” means programmed).

Set OE to “0”, BS2 to “1”, and BS1 to “1”. The status of the Fuse High bits can now be

read at DATA (“0” means programmed).

RDY/BSY

RESET +12V

PAGEL

$40

DATA

XA1

XA0

BS1

XTAL1

$40

DATA

Write Fuse Low byte

Write Fuse high byte

$40

DATA

Write Extended Fuse byte

BS2

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