Action
CHCTRLB.EVACT
CHCTRLB.TRGSRC
Conditional Transfer on Strobe
TRIG
any peripheral
Conditional Transfer
CTRIG
Conditional Block Transfer
CBLOCK
Channel Suspend
SUSPEND
Channel Resume
RESUME
Skip Next Block Suspend
SSKIP
Normal Transfer
The event input is used to trigger a beat or burst transfer on peripherals.
The event is acknowledged as soon as the event is received. When received, both the Channel Pending
status bit in the Channel Status register (
.PEND) and the corresponding Channel n bit in the
.PENDCHn) are set. If the event is received while the channel is
pending, the event trigger is lost.
The figure below shows an example where beat transfers are enabled by internal events.
Figure 26-11. Beat Event Trigger Action
CHENn
Peripheral Trigger
Event
PENDCHn
BUSYCHn
Data Transfer
Trigger Lost
Block Transfer
BEAT
BEAT
BEAT
BEAT
BEAT
BEAT
Block Transfer
Conditional Transfer on Strobe
The event input is used to trigger a transfer on peripherals with pending transfer requests. This event
action is intended to be used with peripheral triggers, e.g. for timed communication protocols or periodic
transfers between peripherals: only when the peripheral trigger coincides with the occurrence of a
(possibly cyclic) event the transfer is issued.
The event is acknowledged as soon as the event is received. The peripheral trigger request is stored
internally when the previous trigger action is completed (i.e. the channel is not pending) and when an
active event is received. If the peripheral trigger is active, the DMA will wait for an event before the
peripheral trigger is internally registered. When both event and peripheral transfer trigger are active, both
.PENDCHn are set. A software trigger will now trigger a transfer.
The figure below shows an example where the peripheral beat transfer is started by a conditional strobe
event action.
Atmel SAM L22G / L22J / L22N [DATASHEET]
Atmel-42402E-SAM L22G / L22J / L22N_Datasheet_Complete-07/2016
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