ATXMEGA256A3_1012 Datasheet, PDF (104/134 Pages) ATMEL Corporation – 8/16-bit XMEGA A3 Microcontroller

8068T–AVR–12/10
XMEGA A3
16. Pending full asynchronous pin change interrupts will not wake the device
Any full asynchronous pin-change Interrupt from pin 2, on any port, that is pending when the
sleep instruction is executed, will be ignored until the device is woken from another source
or the source triggers again. This applies when entering all sleep modes where the System
Clock is stopped.
Problem fix/Workaround
None.
17. Pin configuration does not affect Analog Comparator output
The Output/Pull and inverted pin configuration does not affect the Analog Comparator
output.
Problem fix/Workaround
None for Output/Pull configuration.
For inverted I/O, configure the Analog Comparator to give an inverted result (i.e. connect
positive input to the negative AC input and vice versa), or use and external inverter to
change polarity of Analog Comparator output.
18. NMI Flag for Crystal Oscillator Failure automatically cleared
NMI flag for Crystal Oscillator Failure (XOSCFDIF) will be automatically cleared when exe-
cuting the NMI interrupt handler.
Problem fix/Workaround
This device revision has only one NMI interrupt source, so checking the interrupt source in
software is not required.
19. Writing EEPROM or Flash while reading any of them will not work
The EEPROM and Flash cannot be written while reading EEPROM or Flash, or while exe-
cuting code in Active mode.
Problem fix/Workaround
Enter IDLE sleep mode within 2.5 µs (Five 2 MHz clock cycles and 80 32 MHz clock cycles)
after starting an EEPROM or flash write operation. Wake-up source must either be
EEPROM ready or NVM ready interrupt. Alternatively set up a Timer/Counter to give an
overflow interrupt 7 ms after the erase or write operation has started, or 13 ms after atomic
erase-and-write operation has started, and then enter IDLE sleep mode.
20. Crystal start-up time required after power-save even if crystal is source for RTC
Even if 32.768 kHz crystal is used for RTC during sleep, the clock from the crystal will not be
ready for the system before the specified start-up time. See "XOSCSEL[3:0]: Crystal Oscilla-
tor Selection" in XMEGA A Manual. If BOD is used in active mode, the BOD will be on during
this period (0.5s).
Problem fix/Workaround
If faster start-up is required, go to sleep with internal oscillator as system clock.
21. RTC Counter value not correctly read after sleep
If the RTC is set to wake up the device on RTC Overflow and bit 0 of RTC CNT is identical to
bit 0 of RTC PER as the device is entering sleep, the value in the RTC count register can not
be read correctly within the first prescaled RTC clock cycle after wakeup. The value read will
be the same as the value in the register when entering sleep.
The same applies if RTC Compare Match is used as wake-up source.
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