Return to previous page ｜ Return to menu ｜ Go to next page

● Indirect mode

Indirect mode is used when you want to execute multiple DMA transfers with one startup. In the indirect mode, instead of setting the register as in the direct mode, the DMA is executed by accessing the register via the RAM. As an example, suppose you want to execute the following three DMA transfers continuously at level 0 through the work RAM area (6000000 H ). 
(a) DMA transfer of 20  H  bytes from 4000000  H  to 5C00000  H .
(b) DMA transfer of 10  H  bytes from 5E00000  H  to 6080000  H .
(c) DMA transfer of 15  H  bytes from 5A00000  H  to 6081000  H .
⿟ DMA (indirect mode) can be executed by following the steps below. 
(1) From the work RAM area (6000000  H )
Write data at the position.

Figure 2.8 Data writing example 

 (2) DMA parameter source address in the write address register (D0W)
Write (6000000  H ).
(3) Write the address addition value (101  H ) to the address addition value register D0AD.
(Load the address addition value from CPU to address 25FE000C  H .
The details of the added value are described in the address added value in this section. With normal DMA,
⿟ Specify 101  H  as the address addition value. )
(4) Set the DMA mode to 1, the address update bit and the DMA activation factor as required.
Defined and written to mode / address update / DMA activation factor register D0MD
. For example, address update is set to hold mode and V-blank-IN is the activation factor
If it is, write 1000000  H  to D0MD. (CPU to address
Load 1000000  H  into 25FE0014  H . )

Return to previous page ｜ Return to menu ｜ Go to next page