ATMEGA8L ATMEL [ATMEL Corporation], ATMEGA8L Datasheet - Page 215

• Manufacturer Part Number: ATMEGA8L
• Description: 8-bit AVR with 8K Bytes In-System Programmable Flash
• Manufacturer: ATMEL [ATMEL Corporation]

Preventing Flash Corruption
Programming Time for Flash
when using SPM
2486M–AVR–12/03
During periods of low V
age is 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 cor-
rectly. 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
2. Keep the AVR RESET active (low) during periods of insufficient power supply
3. Keep the AVR core in Power-down sleep mode during periods of low V
The calibrated RC Oscillator is used to time Flash accesses. Table 81 shows the typical
programming time for Flash accesses from the CPU.
Table 81. SPM Programming Time
Symbol
Flash write (page erase, page write,
and write Lock Bits by SPM)
Loader Lock Bits to prevent any Boot Loader software updates.
voltage. This can be done by enabling the internal Brown-out Detector (BOD) if
the operating voltage matches the detection level. If not, an external low V
Reset Protection circuit can be 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.
will prevent the CPU from attempting to decode and execute instructions, effec-
tively protecting the SPMCR Register and thus the Flash from unintentional
writes.
CC,
the Flash program can be corrupted because the supply volt-
Min Programming Time
3.7 ms
Max Programming Time
ATmega8(L)
4.5 ms
CC
. This
CC
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