ATmega328P datasheet(298/345 Pages) ATMEL

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298

7810A–AVR–11/09

ATmega328P [Preliminary]

27.7.11

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. If LB mode 3 is programmed

(LB1 and LB2 is programmed), it is not possible to program the Boot Lock bits by any

External Programming mode.

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

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

27.7.12

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 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).

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

be read at DATA (“0” means programmed).

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

DATA (“0” means programmed).

Set OE to “1”.

Figure 27-6. Mapping Between BS1, BS2 and the Fuse and Lock Bits During Read

27.7.13

Reading the Signature Bytes

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

page 293 for details on Command and Address loading):

A: Load Command “0000 1000”.

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

Set OE to “0”, and BS1 to “0”. The selected Signature byte can now be read at DATA.

Set OE to “1”.

Lock Bits

BS2

Fuse High Byte

BS1

DATA

Fuse Low Byte

BS2

Extended Fuse Byte

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