ATMEGA48V_11 ATMEL [ATMEL Corporation], ATMEGA48V_11 Datasheet - Page 278

• Manufacturer Part Number: ATMEGA48V_11
• Description: 8-bit Atmel Microcontroller with 4/8/16K Bytes In-System Programmable Flash
• Manufacturer: ATMEL [ATMEL Corporation]

27.8.10
2545T–AVR–05/11
Preventing flash corruption
shown below. Refer to
High byte.
When reading the Extended Fuse byte, load 0x0002 in the Z-pointer. When an LPM instruction
is executed within three cycles after the BLBSET and SELFPRGEN 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
Fuse 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.
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 Lock
2. Keep the AVR RESET active (low) during periods of insufficient power supply voltage.
3. Keep the AVR core in Power-down sleep mode during periods of low V
Bit
Rd
Bit
Rd
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.
vent the CPU from attempting to decode and execute instructions, effectively protecting
the SPMCSR Register and thus the Flash from unintentional writes.
FHB7
Table 28-4 on page 286
7
7
–
Table 28-6 on page 287
CC
FHB6
, the Flash program can be corrupted because the supply voltage is
6
6
–
FHB5
5
5
–
for detailed description and mapping of the Extended
FHB4
4
4
–
for detailed description and mapping of the Fuse
FHB3
EFB3
3
3
CC
ATmega48/88/168
FHB2
EFB2
reset protection circuit can be
2
2
FHB1
EFB1
1
1
CC
. This will pre-
FHB0
EFB0
0
0
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