Datasheet

Figure 20-14. Conditional Block Transfer with Beat Peripheral Triggers
BEAT BEAT
Block Transfer
BEAT BEAT
Block Transfer
Data Transfer
Peripheral Trigger
Event
PENDCHn
Channel Suspend
The event input is used to suspend an ongoing channel operation. The event is acknowledged when the
current AHB access is completed. For further details on Channel Suspend, refer to 20.6.3.2 Channel
Suspend.
Channel Resume
The event input is used to resume a suspended channel operation. The event is acknowledged as soon
as the event is received and the Channel Suspend Interrupt Flag (CHINTFLAG.SUSP) is cleared. For
further details refer to 20.6.3.2 Channel Suspend.
Skip Next Block Suspend
This event can be used to skip the next block suspend action. If the channel is suspended before the
event rises, the channel operation is resumed and the event is acknowledged. If the event rises before a
suspend block action is detected, the event is kept until the next block suspend detection. When the block
transfer is completed, the channel continues the operation (not suspended) and the event is
acknowledged.
Related Links
24.8.3 USER
20.6.3.5 Event Output Selection
Event output selection is available only for the least significant DMA channels. The pulse width of an
event output from a channel is one AHB clock cycle.
The output of channel events is enabled by writing a '1' to the Channel Event Output Enable bit in the
Control B register (CHCTRLB.EVOE). The event output cause is selected by writing to the Event Output
Selection bits in the Block Transfer Control register (BTCTRL.EVOSEL). It is possible to generate events
after each block transfer (BTCTRL.EVOSEL=0x1) or beat transfer (BTCTRL.EVOSEL=0x3). To enable an
event being generated when a transaction is complete, the block event selection must be set in the last
transfer descriptor only.
Figure 20-15 shows an example where the event output generation is enabled in the first block transfer,
and disabled in the second block.
SAM D21 Family
DMAC – Direct Memory Access Controller
© 2018 Microchip Technology Inc.
Datasheet Complete
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