Dma Transfer - Nintendo 1504166 - Game Boy Advance SP Edition Console Programming Manual

AGB Programming Manual

12 DMA Transfer

AGB has 4 DMA transfer channels.
The highest priority of these channels is DMA0, followed in order by DMA1, DMA2, and DMA3.
If a DMA with a higher priority than the currently executing DMA begins execution, the execution
of the current DMA is temporarily halted, and the DMA with the higher priority is executed. Once
this DMA finishes, the original DMA resumes execution from where it was halted.
Thus, the most appropriate uses of each DMA channel are those described below.
Ø DMA 0
Because this has the highest priority, it is not interrupted by other DMA channels.
Thus, it is used for reliable processing over a limited period, as is required for
purposes such as horizontal-blanking DMA.
Ø DMA 1 and DMA 2
These are used for direct sound functions, which require relatively high priority, or for
general-purpose transfers.
Ø DMA 3
This is used for the most general types of transfers.
Perform the following settings when using DMA.
1. Specify the transfer source address in the source address register.
2. Specify the transfer destination address in the destination address register.
3. Set the number of data items in the word-count register.
4. Specify the transfer method to be used in the DMA control register.
[Cautions for DMA]
When transferring data to OAM or OBJ VRAM by DMA during H-blanking, the H-blank must
first be freed from OBJ display hardware processing periods using the DISPCNT register.
(See "5 Image System".)
©1999 - 2001 Nintendo of America Inc.
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DMA Transfer
D.C.N. AGB-06-0001-002B4