AT90S4414/8515
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Programming the Lock Bits
The algorithm for programming the Lock bits is as follows (refer to Programming the Flash for details on Command and
Data loading):
1. A: Load Command “0010 0000”.
2. D: Load Data Low Byte. Bit n = ‘0’ programs the Lock bit.
Bit 2 = Lock Bit2
Bit 1 = Lock Bit1
Bit 7-3,0 = “1”. These bits are reserved and should be left unprogrammed (“1”).
3. E: Write Data Low Byte.
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 for details on Command
loading):
1. A: Load Command “0000 0100”.
2. Set OE
to “0”, and BS to “1”. The status of the Fuse and Lock bits can now be read at DATA (“0” means
programmed).
Bit 7 = Lock Bit1
Bit 6 = Lock Bit2
Bit 5 = SPIEN Fuse bit
Bit 0 = FSTRT Fuse bit
3. Set OE
to “1”.
Observe that BS needs to be set to “1”.
Reading the Signature Bytes
The algorithm for reading the Signature bytes is as follows (refer to Programming the Flash for details on Command and
Address loading):
1. A: Load Command “0000 1000”.
2. C: Load Address Low Byte ($00 - $02).
Set OE
to “0”, and BS to “0”. The selected Signature byte can now be read at DATA.
3. Set OE
to “1”.
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