Datasheet

29.7.9 Programming the Fuse High Bits
The algorithm for programming the Fuse High bits is as follows (Please refer to Programming the Flash
for details on Command and Data loading):
1. Step A: Load Command “0100 0000”.
2. Step C: Load Data Low Byte. Bit n = “0” programs and bit n = “1” erases the Fuse bit.
3. Set BS1 to “1” and BS2 to “0”. This selects high data byte.
4. Give WR a negative pulse and wait for RDY/BSY to go high.
5. Set BS1 to “0”. This selects low data byte.
29.7.10 Programming the Lock Bits
The algorithm for programming the Lock bits is as follows (Please refer to Programming the Flash for
details on Command and Data loading):
1. Step A: Load Command “0010 0000”.
2. Step C: Load Data Low Byte. Bit n = “0” programs the Lock bit.
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.
29.7.11 Reading the Fuse and Lock Bits
The algorithm for reading the Fuse and Lock bits is as follows (Please refer to Programming the Flash for
details on Command loading):
1. Step A: Load Command “0000 0100”.
2. 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).
3. 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).
4. 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).
5. Set OE to “1”.
Figure 29-5. Mapping Between BS1, BS2 and the Fuse and Lock Bits During Read
Fuse low byte
Lock bits
0
1
BS2
Fuse high byte
0
1
BS1
DATA
29.7.12 Reading the Signature Bytes
The algorithm for reading the Signature bytes is as follows (Please refer to Programming the Flash for
details on Command and Address loading):
AVR 8-Bit Microcontroller
MEMPROG- Memory Programming
© 2017 Microchip Technology Inc.
Datasheet Complete
40001974A-page 299