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Chapter 26  DMA Controller

4.Operation Flowcharts

Load the initial address,

transfer count, and

number of blocks

Activation request

wait

DMA transfer end

DMA interrupted

DTC=0

DMA stop

DENB=1

DENB=>0

Write back the address,

transfer count, and number

of blocks

Interrupt clear

Activation request

One-time access for fly-by

Reload enable

Only when the peripheral interrupt
activation source is selected

Calculate the address for

transfer source address access

Calculate the address for transfer

destination address access

Number of transfer - 1

Interrupt cleared

None

Demand transfer
-  Only requests (level detection) from the external pin (DREQ) are accepted. Activation by 

other sources is disabled.

-  Access to an external area is required (since access to an external area becomes the 

next activation source).

-  The number of blocks is always 1, regardless of the settings.
-  Interrupt clear and the DMA interrupt are issued when transfer for the number of times 

specified is completed.