Rainbow Electronics ATmega128L - Manual (Page 289)

289
ATmega128(L)
2467B–09/01
Programming the Fuse High
Bits The algorithm for programming the Fuse high bits is as follows (refer to “Programming
the Flash” on page 285 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 BS1 to '1'. 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.
Programming the Extended
Fuse Bits The algorithm for programming the Extended Fuse bits is as follows (refer to “Program-
ming the Flash” on page 285 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 to “1” and BS1 to “0”. This selects extended data byte.
4. Give WR a negative pulse and wait for RDY/BSY to go high.
5. Set BS2 to “0”. This selects low data byte.
Programming the Lock Bits The algorithm for programming the Lock bits is as follows (refer to “Programming the
Flash” on page 285 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.
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.
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 285 for details on Command loading):
1. 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 “1” and BS1 to “0”. The status of the Extended Fuse bits
can now be read at DATA (“0” means programmed).
5. 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).
6. Set OE to “1”.