ATMEGA2561V ATMEL [ATMEL Corporation], ATMEGA2561V Datasheet - Page 332

• Manufacturer Part Number: ATMEGA2561V
• Description: 8-bit Microcontroller with 64K/128K/256K Bytes In-System Programmable Flash
• Manufacturer: ATMEL [ATMEL Corporation]

Preventing Flash Corruption
Programming Time for Flash
when Using SPM
332
ATmega640/1280/1281/2560/2561
CPU cycles. When SIGRD and SPMEN are cleared, LPM will work as described in the
Instruction set Manual.
Table 138. Signature Row Addressing
Note:
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 139 shows the typi-
cal programming time for Flash accesses from the CPU.
Table 139. SPM Programming Time
Signature Byte
Device Signature Byte 1
Device Signature Byte 2
Device Signature Byte 3
RC Oscillator Calibration Byte
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 SPMCSR Register and thus the Flash from unintentional
writes.
All other addresses are reserved for future use.
Symbol
CC
, the Flash program can be corrupted because the supply volt-
Min Programming Time
3.7 ms
Z-Pointer Address
0x0000
0x0002
0x0004
0x0001
Max Programming Time
4.5 ms
2549K–AVR–01/07
CC
. This
CC