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DMA channel #0
Source #1
Source #2
Source #3
Always #1
DMA channel #m-1
Always #y
Trigger #m
Source #x
Trigger #1
Figure 20-2. DMAMUX triggered channels
The DMA channel triggering capability allows the system to schedule regular DMA
transfers, usually on the transmit side of certain peripherals, without the intervention of
the processor. This trigger works by gating the request from the peripheral to the DMA
until a trigger event has been seen. This is illustrated in the following figure.
DMA request
Peripheral request
Trigger
Figure 20-3. DMAMUX channel triggering: normal operation
After the DMA request has been serviced, the peripheral will negate its request,
effectively resetting the gating mechanism until the peripheral reasserts its request and
the next trigger event is seen. This means that if a trigger is seen, but the peripheral is not
requesting a transfer, then that trigger will be ignored. This situation is illustrated in the
following figure.
Functional description
KL27 Sub-Family Reference Manual , Rev. 5, 01/2016
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Freescale Semiconductor, Inc.