19.5.6 Events

The DMAC can generate the following events:

Table 19-2. DMAC Event Generators
Generator Name		Description	Event Type	Generating Clock Domain	Length of Event
Peripheral	Event	Description	Event Type	Generating Clock Domain	Length of Event
DMAC	CH_n	Transfer on channel n is complete	Pulse	CLK_DMAC_AHB	One CLK_DMAC_AHB period

Writing a ‘1’ to the Channel Event Output Enable bit in the Channel Control B (CHCTRLB.EVOE) register enables the corresponding event output. Writing a ‘0’ to this bit disables the corresponding event output.

The event output cause is selected by writing to the Event Output Selection bits in the Block Transfer Control (BTCTRL.EVOSEL) register. It is possible to generate events after each block transfer (BTCTRL.EVOSEL = 0x1) or after each beat transfer (BTCTRL.EVOSEL = 0x3). To enable the generation of an event when a transaction is complete, the block event selection must be set only in the last transfer descriptor.

Note: Only the 2 lowest-numbered DMA channels can be configured as event output generators.

Figure 19-12 shows an example where the event output generation is enabled for the first block transfer and disabled for the second block.

The DMAC can connect to the following events:

Table 19-3. Event Users
User Name		Description	Input Detection	Channel Path Type
Peripheral	Input	Description	Input Detection	Channel Path Type
DMAC	CH_n	Channel n	Level	Asynchronous Synchronous Resynchronized

Writing a ‘1’ to a Channel Event Input Enable bit in the Channel Control B register (CHCTRLB.EVIE) enables the corresponding action on input event. Writing a ‘0’ to this bit disables the corresponding action on input event.

Note: Only the 2 lowest-numbered DMA channels can be configured as event users.

The event users can trigger the following actions:

Table 19-4. Event Actions
Event Input	Event Action	Description
CH_n	TRIG	Normal transfer or conditional transfer on strobe triggered by an event
	CTRIG	Conditional transfer triggered by an event
	CBLOCK	Conditional block transfer triggered by an event
	SUSPEND	Suspends a channel's operation on event
	RESUME	Resumes a suspended channel's operation on event
	SSKIP	Skips the next block suspend action

Refer to the EVSYS - Event System chapter for details on configuring the event system.