atmega32c1 ATMEL Corporation, atmega32c1 Datasheet - Page 283

• Manufacturer Part Number: atmega32c1
• Description: Atmega32m1 Automotive 8-bit Avr Microcontroller With 32k/64k Bytes In-system Programmable Flash
• Manufacturer: ATMEL Corporation

23.7.10
23.7.11
7647A–AVR–02/08
Reading the Signature Row from Software
Preventing Flash Corruption
value of the Extended Fuse byte (EFB) will be loaded in the destination register as shown below.
Refer to
byte.
Fuse and Lock bits that are programmed, will be read as zero. Fuse and Lock bits that are
unprogrammed, will be read as one.
To read the Signature Row from software, load the Z-pointer with the signature byte address
given in
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 Lock bits 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.
Table 23-5.
Note:
During periods of low V
too low for the CPU and the Flash to operate properly. These issues are the same as for board
level systems using the Flash, and the same design solutions should be applied.
A Flash program corruption can be caused by two situations when the voltage is too low. First, a
regular write sequence to the Flash requires a minimum voltage to operate correctly. Secondly,
the CPU itself can execute instructions incorrectly, if the supply voltage for executing instructions
is too low.
Flash corruption can easily be avoided by following these design recommendations (one is
sufficient):
1. If there is no need for a Boot Loader update in the system, program the Boot Loader
2. Keep the AVR RESET active (low) during periods of insufficient power supply voltage.
Bit
Rd
Signature Byte
Device Signature Byte 1
Device Signature Byte 2
Device Signature Byte 3
RC Oscillator Calibration Byte
TSOFFSET Temp Sensor Offset
TSGAIN Temp Sensor Gain
Lock bits to prevent any Boot Loader software updates.
This can be done by enabling the internal Brown-out Detector (BOD) if the operating volt-
age matches the detection level. If not, an external low V
used. If a reset occurs while a write operation is in progress, the write operation will be
completed provided that the power supply voltage is sufficient.
All other addresses are reserved for future use.
Table 23-5 on page 283
Table 24-4 on page 290
Signature Row Addressing
7
–
CC
, the Flash program can be corrupted because the supply voltage is
6
–
and set the SIGRD and SPMEN bits in SPMCSR. When an
for detailed description and mapping of the Extended Fuse
5
–
4
–
EFB3
3
ATmega32/64/M1/C1
CC
EFB2
reset protection circuit can be
2
Z-Pointer Address
0x0000
0x0002
0x0004
0x0001
0x0003
0x0005
EFB1
1
EFB0
0
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