10 reading the signature row from software, Atmega128rfa1 – Rainbow Electronics ATmega128RFA1 User Manual
Page 457
457
8266A-MCU Wireless-12/09
ATmega128RFA1
Bit
7
6
5
4
3
2
1
0
Rd
-
-
BLB12
BLB11
BLB02
BLB01
LB2
LB1
The algorithm for reading the Fuse Low byte is similar to the one described above for
reading the Lock bits. To read the Fuse Low byte, load the Z-pointer with 0x0000 and
set the BLBSET and SPMEN bits in SPMCSR. When an (E)LPM instruction is executed
within three cycles after the BLBSET and SPMEN bits are set in the SPMCSR, the
value of the Fuse Low byte (FLB) will be loaded in the destination register as shown on
the next page. Refer to (see
) for a detailed description and
mapping of the Fuse Low byte.
Bit
7
6
5
4
3
2
1
0
Rd
FLB7
FLB6
FLB5
FLB4
FLB3
FLB2
FLB1
FLB0
Similarly, load 0x0003 in the Z-pointer for reading the Fuse High byte. When an (E)LPM
instruction is executed within three cycles after the BLBSET and SPMEN bits are set in
the SPMCSR, the value of the Fuse High byte (FHB) will be loaded in the destination
register as shown below. Refer to
for detailed description and
mapping of the Fuse High byte.
Bit
7
6
5
4
3
2
1
0
Rd
FHB7
FHB6
FHB5
FHB4
FHB3
FHB2
FHB1
FHB0
Load 0x0002 in the Z-pointer for reading the Extended Fuse byte. When an (E)LPM
instruction is executed within three cycles after the BLBSET and SPMEN bits are set in
the SPMCSR, the value of the Extended Fuse byte (EFB) will be loaded in the
destination register as shown below. Refer to
Table 31-3 on page 465
for detailed
description and mapping of the Extended Fuse byte.
Bit
7
6
5
4
3
2
1
0
Rd
-
-
-
-
-
EFB2
EFB1
EFB0
Fuse and Lock bits that are programmed will be read as zero. Fuse and Lock bits that
are un-programmed will be read as one.
30.6.10 Reading the Signature Row from Software
To read the Signature Row from software, load the Z-pointer with the signature byte
address given in
and set the SIGRD and SPMEN bits in SPMCSR.
When a LPM instruction is executed within three CPU cycles after the SIGRD and
SPMEN bits are set in SPMCSR, the signature byte value will be loaded in the
destination register. The SIGRD and SPMEN bits will auto-clear upon completion of
reading the Signature Row or if no LPM instruction is executed within three CPU cycles.
When SIGRD and SPMEN are cleared, LPM will work as described in the Instruction
Set Manual. The Signature Row cannot be read during an EEPROM write/erase
operation.
Table 30-3. Signature Row Addressing
Signature Byte
Z-Pointer Address
Device Signature Byte 1
0x0000
Device Signature Byte 2
0x0002
Device Signature Byte 3
0x0004
RC Oscillator Calibration Byte
0x0001
Note:
2. All other addresses are reserved for future use.