MAC7200 datasheet(565/976 Pages) FREESCALE

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Functional Description

MAC7200 Microcontroller Family Reference Manual, Rev. 2

Freescale Semiconductor

487

Figure 27-3. DMA Mux Channel 0-7 Block Diagram

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 Figure 27-4.

Figure 27-4. DMA Mux Channel Triggering: Normal Operation

Once the DMA request has been serviced, the peripheral will negate its request, effectively resetting the

gating mechanism until the peripheral re-asserts 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, that triggered will be ignored. This

situation is illustrated in Figure 27-5.

Source #1

Source #2

Source #3

Source #30

DMA Channel #0

DMA Channel #1

DMA Channel #2

DMA Channel #3

DMA Channel #4

DMA Channel #5

DMA Channel #6

DMA Channel #7

Trigger #2

Trigger #3

Trigger #1

Trigger #4

Trigger #5

Trigger #6

Trigger #7

Trigger #8

Periph Request

Trigger

DMA Request

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