Datasheet

310
XMEGA D4 [DATASHEET]
8135P–AVR–01/2014
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 neg-
ative 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 executing 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 enter-
ing 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 Oscillator 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.