MAC7200 datasheet(567/976 Pages) FREESCALE

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Functional Description

MAC7200 Microcontroller Family Reference Manual, Rev. 2

Freescale Semiconductor

489

Figure 27-6. DMA Mux Channel 8-15 Block Diagram

27.4.3

"Always Enabled" DMA Sources

In addition to the 30 peripherals that can be used as DMA sources, there are 8 additional DMA sources

that are "always enabled". Unlike the peripheral DMA sources, where the peripheral controls the flow of

data during DMA transfers, the "always enabled" sources provide no such "throttling" of the data transfers.

These sources are most useful in the following cases:

•

Doing DMA transfers to/from GPIO - Moving data from/to one or more GPIO pins, either

un-throttled (i.e.-as fast as possible), or periodically (using the DMA triggering capability).

•

Doing DMA transfers from memory to memory - Moving data from memory to memory, typically

as fast as possible, sometimes with software activation.

•

Doing DMA transfers from memory to the external bus (or vice-versa) - Similar to memory to

memory transfers, this is typically done as quickly as possible.

•

Any DMA transfer that requires software activation - Any DMA transfer that should be explicitly

started by software.

In cases where software should initiate the start of a DMA transfer, a "always enabled" DMA source can

be used to provide maximum flexibility. When activating a DMA channel via software, subsequent

Source #1

Source #2

Source #3

Source #30

DMA Channel #8

DMA Channel #9

DMA Channel #10

DMA Channel #11

DMA Channel #12

DMA Channel #13

DMA Channel #14

DMA Channel #15

MAC7200 Datasheet(PDF) 567 Page - Freescale Semiconductor, Inc