22.5.4 DMA
- Overflow (OVF): A DMA request is generated when an update condition (overflow, underflow or retrigger) is detected. The request is cleared by hardware upon DMA acknowledge.
- Match or Capture Channel n (MCn): For a compare channel, the DMA request is generated on each compare match detection and is cleared by hardware on the DMA acknowledge. For a capture channel, the DMA request is generated when valid data is present in the CC[n] register and is cleared when the CC[n] register is read.
The TC can change its DMA request trigger behavior by setting the DMA One-shot Trigger Mode
bit in the Control A (CTRLA.DMAOS) register. In one-shot mode, DMA requests will only be
generated on an OVF condition after writing ‘0x5’ to the Command bit field of
the Control B Set (CTRLBSET.CMD) register. After a request is generated, another one-shot
command must be issued to generate a subsequent OVF DMA request. Issuing multiple one-shot
commands before an OVF condition occurs has no effect and the TC will only generate one DMA
request once the OVF condition occurs.
0x5), a request will only be generated on the next OVF
condition. Any OVF condition that occurred before writing the command will not have any
effect.1’ MCn DMA requests are
disabled.The DMA request lines are connected to the DMA Controller (DMAC). Using the TC DMA requests needs to have the DMAC configured first. Refer to the DMAC – Direct Memory Access Controller chapter for details.