ATXMEGA16A4_14 Datasheet, PDF (97/108 Pages) ATMEL Corporation – Non-volatile Program and Data Memories

8069R–AVR–06/2013
XMEGA A4
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.
17. 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.
18. Flash Power Reduction Mode can not be enabled when entering sleep
If Flash Power Reduction Mode is enabled when entering Power-save or Extended Standby
sleep mode, the device will only wake up on every fourth wake-up request. If Flash Power
Reduction Mode is enabled when entering Idle sleep mode, the wake-up time will vary with
up to 16 CPU clock cycles.
Problem fix/Workaround
Disable Flash Power Reduction mode before entering sleep mode.
19. 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.
20. 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.
Problem fix/Workaround
Wait at least one prescaled RTC clock cycle before reading the RTC CNT value.
21. Pending asynchronous RTC-interrupts will not wake up device
Asynchronous Interrupts from the Real-Time-Counter 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.
Problem fix/Workaround
None.
22. TWI Transmit collision flag not cleared on repeated start
The TWI transmit collision flag should be automatically cleared on start and repeated start,
but is only cleared on start.
Problem fix/Workaround
Clear the flag in software after address interrupt.
97
Not recommended for new designs -
Use XMEGA A4U series