Datasheet

408
XMEGA D3 [DATASHEET]
Atmel-8134N-ATxmega32D3-64D3-128D3-192D3-256D3-384D3_datasheet–03/2014
16. 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.
17. 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 wake-up. 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.
18. 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.
19. 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.
20. Clearing TWI Stop Interrupt Flag may lock the bus
If software clears the STOP Interrupt Flag (APIF) on the same Peripheral Clock cycle as the hardware sets
this flag due to a new address received, CLKHOLD is not cleared and the SCL line is not released. This will
lock the bus.
Problem fix/Workaround
Check if the bus state is IDLE. If this is the case, it is safe to clear APIF. If the bus state is not IDLE, wait for
the SCL pin to be low before clearing APIF.
Code:
/* Only clear the interrupt flag if within a "safe zone". */
while ( /* Bus not IDLE: */
((COMMS_TWI.MASTER.STATUS & TWI_MASTER_BUSSTATE_gm) !=
TWI_MASTER_BUSSTATE_IDLE_gc)) &&
/* SCL not held by slave: */
!(COMMS_TWI.SLAVE.STATUS & TWI_SLAVE_CLKHOLD_bm)
)
{
/* Ensure that the SCL line is low */