DMA programming examples

AN3117

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Doc ID 16846 Rev 4

Transfer results are shown in Table 11.

4.6.2

Transfer example case 2: software priority configuration 1 of the DMA



channels

In this example, the software priority of the channels is updated as shown in Table 12.

Figure 9.

Example case 2: DMA channel data transfers as a function of time

Table 11.

Results of example case 1

Time

RAM Buffer1

TIM1 ARRL

TIM2 ARRL

TIM3 ARRL

TIM4 ARR

RAM Buffer2

t0

0x00

0x11

0x22

0x33

0x44

0x55

t1

-

-

-

0x55

-

-

t2

-

-

0x00

-

-

-

t3

0x11

-

-

-

-

-

t4

-

-

-

-

-

0x44

Result

0x11

0x11

0x00

0x55

0x44

0x44

Table 12.

Example case 2:

priority configuration of the DMA channels

DMA channel

HW priority

SW priority

Channel 0

Very high

Low

Channel 1

High

High

Channel 2

Medium

Very high

Channel 3

Low

Medium

time

t0

t1

t2

t3

t4

ai17424

Hardware priority

Channel 0

Channel 1

Channel 2

Channel 3

Transfer C

Transfer B

Transfer D

Transfer A