Datasheet

253
ATmega48/88/168 Automotive [DATASHEET]
7530K–AVR–07/14
25.7.12 Reading the Fuse and Lock Bits
The algorithm for reading the fuse and lock bits is as follows (refer to Section 25.7.4 “Programming the Flash” on page 248
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”.
Figure 25-6. Mapping Between BS1, BS2 and the Fuse and Lock Bits During Read
25.7.13 Reading the Signature Bytes
The algorithm for reading the signature bytes is as follows (refer to Section 25.7.4 “Programming the Flash” on page 248 for
details on command and address loading):
1. A: Load command “0000 1000”.
2. B: Load address low byte (0x00 - 0x02).
3. Set OE
to “0”, and BS1 to “0”. The selected signature byte can now be read at DATA.
4. Set OE
to “1”.
25.7.14 Reading the Calibration Byte
The algorithm for reading the calibration byte is as follows (refer to Section 25.7.4 “Programming the Flash” on page 248 for
details on command and address loading):
1. A: Load command “0000 1000”.
2. B: Load address low byte, 0x00.
3. Set OE
to “0”, and BS1 to “1”. The calibration byte can now be read at DATA.
4. Set OE
to “1”.
Extended Fuse Byte
0
1
Fuse Low Byte
BS2
Fuse High Byte
0
1
Lock Bits
BS2
BS1
DATA
0
1