ATmega325P datasheet(282/364 Pages) ATMEL

282 / 364 page

282

8023F–AVR–07/09

ATmega325P/3250P

Figure 25-5. Programming the FUSES Waveforms

25.6.11

Programming the Lock Bits

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

page 277 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.

25.6.12

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 277 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”.

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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