ATMEGA640 datasheet(335/436 Pages) MICROCHIP

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ATmega640/V-1280/V-1281/V-2560/V-2561/V [DATASHEET]

DS40002211A

30.7.9

Programming the Fuse High Bits

The algorithm for programming the Fuse High bits is as follows (refer to “Programming the Flash” on page 331 for

details on Command and Data loading):

1. A: Load Command “0100 0000”.

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

3. Set BS2, BS1 to “01”. This selects high data byte.

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

5. Set BS2, BS1 to “00”. This selects low data byte.

30.7.10

Programming the Extended Fuse Bits

The algorithm for programming the Extended Fuse bits is as follows (refer to “Programming the Flash” on page 331

for details on Command and Data loading):

1. 1. A: Load Command “0100 0000”.

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

3. 3. Set BS2, BS1 to “10”. This selects extended data byte.

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

5. 5. Set BS2, BS1 to “00”. This selects low data byte.

Figure 30-5. Programming the FUSES Waveforms

30.7.11

Programming the Lock Bits

The algorithm for programming the Lock bits is as follows (refer to “Programming the Flash” on page 331 for details

on Command and Data loading):

1. A: Load Command “0010 0000”.

2. C: Load Data Low Byte. Bit n = “0” programs the Lock bit. If LB mode 3 is programmed (LB1 and LB2 is pro-

grammed), it is not possible to program the Boot Lock bits by any External Programming mode.

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

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

RDY/BSY

RESET +12V

PAGEL

0x40

DATA

XA1

XA0

BS1

XTAL1

0x40

DATA

Write Fuse Low byte

Write Fuse high byte

0x40

DATA

Write Extended Fuse byte

BS2

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