Flush Operation Priority
- When a flush request occurs on a suspended channel, if there are pending bytes in
the FIFO, they are written out to memory, XDMAC_CISx.FIS is set. If the FIFO is
empty, XDMAC_CISx.FIS is also set.
- If the flush operation is performed after a disable request, the flush command is
ignored. XDMAC_CISx.FIS is not set.