ATmega325PA Atmel Corporation, ATmega325PA Datasheet - Page 276

• Manufacturer Part Number: ATmega325PA
• Manufacturer: Atmel Corporation

26.8.10
26.8.11
8285D–AVR–06/11
Preventing Flash Corruption
Programming Time for Flash when Using SPM
ATmega165A/PA/325A/PA/3250A/PA/645A/P/6450A/P
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
The calibrated RC Oscillator is used to time Flash accesses.
gramming time for Flash accesses from the CPU.
Table 26-5.
Flash write (Page Erase, Page Write, and
write Lock bits by SPM)
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.
SPM Programming Time
Symbol
CC
, the Flash program can be corrupted because the supply voltage is
Min Programming Time
3.7ms
CC
Table 26-5
reset protection circuit can be
Max Programming Time
shows the typical pro-
CC
. This will pre-
4.5ms
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