RM0046 DMA Channel Mux (DMA_MUX)
Doc ID 16912 Rev 5 431/936
Figure 203. DMA mux channel triggering: ignored trigger
This triggering capability may be used with any peripheral that supports DMA transfers, and
is most useful for two types of situations:
● Periodically polling external devices on a particular bus. As an example, the transmit
side of an SPI is assigned to a DMA channel with a trigger, as described above. Once
setup, the SPI will request DMA transfers (presumably from memory) as long as its
transmit buffer is empty. By using a trigger on this channel, the SPI transfers can be
automatically performed every 5 µs (as an example). On the receive side of the SPI,
the SPI and DMA can be configured to transfer receive data into memory, effectively
implementing a method to periodically read data from external devices and transfer the
results into memory without processor intervention.
● Using the GPIO Ports to drive or sample waveforms. By configuring the DMA to transfer
data to one or more GPIO ports, it is possible to create complex waveforms using
tabular data stored in on-chip memory. Conversely, using the DMA to periodically
transfer data from one or more GPIO ports, it is possible to sample complex waveforms
and store the results in tabular form in on-chip memory.
A more detailed description of the capability of each trigger (for example, resolution, range
of values, etc.) may be found in 30, “Periodic Interrupt Timer (PIT).
Peripheral Request
Tr i gger
DMA Request
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