Data Sheet

287
Atmel | SMART SAM D21 [DATASHEET]
Atmel-42181G–SAM-D21_Datasheet–09/2015
Figure 19-12.Periodic Event with Beat Peripheral Triggers
Conditional transfer: When the conditional transfer event action is selected, the event input is used to trigger a
conditional transfer on peripherals with pending transfer requests. As example, this type of event can be used for
peripheral to peripheral transfers, where one peripheral is source of event and the second peripheral is source of DMA
trigger.
The peripheral Trigger Source must be set in Channel Control B register (CHCTRLB.TRIGSRC). Each peripheral trigger
is stored internally when the event is received. When the peripheral trigger is stored internally, the Channel Pending
status bit is set (CHSTATUS.PEND) and the event is acknowledged. A software trigger will now trigger a transfer.
Figure 19-13 shows an example where conditional event is enabled with peripheral beat trigger requests.
Figure 19-13.Conditional Event with Beat Peripheral Triggers
Conditional block transfer: When the conditional block event action is selected, the event input is used to trigger a
conditional block transfer on peripherals. The peripheral Trigger Source must be set in Channel Control B register
(CHCTRLB.TRIGSRC).
Before starting transfers within a block, an event must be received. When received, the event is acknowledged when the
block transfer is completed. A software trigger will trigger a transfer.
Figure 19-14 shows an example where conditional event block transfer is enabled with peripheral beat trigger requests.
Figure 19-14.Conditional Block Transfer with Beat Peripheral Triggers
Trigger LostTrigger Lost
BEAT
Peripheral Trigger
PENDCHn
Event
Block Transfer
Data Transfer
BEAT BEAT
Event
Peripheral Trigger
PENDCHn
Data Transfer
Block Transfer
BEAT BEAT
Block Transfer
BEAT BEAT
Block Transfer
Data Transfer
Peripheral Trigger
Event
PENDCHn