ATMEGA640 datasheet(336/436 Pages) MICROCHIP

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

DS40002211A

30.7.12

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 331 for

details on Command loading):

1. A: Load Command “0000 0100”.

2. Set OE to “0”, and BS2, BS1 to “00”. The status of the Fuse Low bits can now be read at DATA (“0” means

programmed).

3. Set OE to “0”, and BS2, BS1 to “11”. The status of the Fuse High bits can now be read at DATA (“0” means

programmed).

4. Set OE to “0”, and BS2, BS1 to “10”. The status of the Extended Fuse bits can now be read at DATA (“0”

means programmed).

5. Set OE to “0”, and BS2, BS1 to “01”. The status of the Lock bits can now be read at DATA (“0” means

programmed).

6. Set OE to “1”.

Figure 30-6. Mapping Between BS1, BS2 and the Fuse and Lock Bits During Read

30.7.13

Reading the Signature Bytes

The algorithm for reading the Signature bytes is as follows (refer to “Programming the Flash” on page 331 for

details on Command and Address loading):

1. A: Load Command “0000 1000”.

2. B: Load Address Low Byte (0x00 - 0x02).

3. Set OE to “0”, and BS to “0”. The selected Signature byte can now be read at DATA.

4. Set OE to “1”.

30.7.14

Reading the Calibration Byte

The algorithm for reading the Calibration byte is as follows (refer to “Programming the Flash” on page 331 for

details on Command and Address loading):

1. A: Load Command “0000 1000”.

2. B: Load Address Low Byte, 0x00.

3. Set OE to “0”, and BS1 to “1”. The Calibration byte can now be read at DATA.

4. Set OE to “1”.

Lock Bits

BS2

Fuse High Byte

BS1

DATA

Fuse Low Byte

BS2

Extended Fuse Byte

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