ATMEGA1281V ATMEL [ATMEL Corporation], ATMEGA1281V Datasheet - Page 32

• Manufacturer Part Number: ATMEGA1281V
• Description: 8-bit Atmel Microcontroller with 64K/128K/256K Bytes In-System Programmable Flash
• Manufacturer: ATMEL [ATMEL Corporation]

11.12 ATmega2560 rev. A
2549NS–AVR–05/11
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1.
2. Part does not work under 2.4 volts
3. Incorrect ADC reading in differential mode
4. Internal ADC reference has too low value
5. IN/OUT instructions may be executed twice when Stack is in external RAM
Non-Read-While-Write area of flash not functional
Part does not work under 2.4 volts
Incorrect ADC reading in differential mode
Internal ADC reference has too low value
IN/OUT instructions may be executed twice when Stack is in external RAM
EEPROM read from application code does not work in Lock Bit Mode 3
The Non-Read-While-Write area of the flash is not working as expected. The problem is
related to the speed of the part when reading the flash of this area.
Problem Fix/Workaround
- Only use the first 248K of the flash.
- If boot functionality is needed, run the code in the Non-Read-While-Write area at maximum
1/4th of the maximum frequency of the device at any given voltage. This is done by writing
the CLKPR register before entering the boot section of the code.
The part does not execute code correctly below 2.4 volts.
Problem Fix/Workaround
Do not use the part at voltages below 2.4 volts.
The ADC has high noise in differential mode. It can give up to 7 LSB error.
Problem Fix/Workaround
Use only the 7 MSB of the result when using the ADC in differential mode.
The internal ADC reference has a value lower than specified.
Problem Fix/Workaround
- Use AVCC or external reference.
- The actual value of the reference can be measured by applying a known voltage to the
ADC when using the internal reference. The result when doing later conversions can then be
calibrated.
If either an IN or an OUT instruction is executed directly before an interrupt occurs and the
stack pointer is located in external ram, the instruction will be executed twice. In some cases
this will cause a problem, for example:
- If reading SREG it will appear that the I-flag is cleared.
- If writing to the PIN registers, the port will toggle twice.
- If reading registers with interrupt flags, the flags will appear to be cleared.
Non-Read-While-Write area of flash not functional
ATmega640/1280/1281/2560/2561
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