25.5.3.6 Event Output Selection

The event output selections are available only for channels supporting event outputs.

The Channel Event Output Enable can be set in the corresponding Channel n Event Control register (CHEVCTRL.EVOE). The Event Output Mode bits in Channel n Event Control register (CHEVCTRL.EVOMODE) selects the event type the channel should generate.

The transfer events (CHEVCTRL.EVOMODE = DEFAULT) are strobe events and their duration is one CLK_DMAC_AHB clock period. The transfer event type selection is available in each Descriptor Block Control location (BTCTRL.EVOSEL). Block or burst event output generation is supported.

The trigger action event (CHEVCTRL.EVOMODE = TRIGACT) is a level, active while the trigger action execution is not completed.

Block event output

When the block event output is selected, an event strobe is generated when the block transfer is completed. The pulse width of a block event output from a channel is one AHB clock cycle. It is also possible to use this event type to generate an event when the transaction is complete. For this type of application, the block event selection must be set in the last transfer descriptor only, as shown below.

Burst event output

When the burst event output is selected, an event strobe is generated when each burst transfer within the corresponding block is completed. The pulse width of a burst event output from a channel is one AHB clock cycle. The figure below shows an example where the burst event output is set in the second descriptor of a linked list.

Trigger action event output

When the trigger action event output is selected, an event level is generated. Then event output is set when the transfer trigger occurred, and cleared when the corresponding trigger action is completed. The figure below shows an example for each trigger action type.