REUSING SPRITE DMA CHANNELS
Each of the eight sprite DMA channels can produce more than one independently
controllable image. There may be times when you want more than eight objects, or you
may be left with fewer than eight objects because you have attached some of the sprites
to produce more colors or larger objects or overlapped some to produce more complex
images. You can reuse each sprite DMA channel several times within the same display
field, as shown in Figure 4-9.
Figure 4-9: (Typical Example of Sprite Reuse)
In single-sprite usage, two all-zero words are placed at the end of the data structure to
stop the DMA channel from retrieving any more data for that particular sprite during that
display field. To reuse a DMA channel, you replace this pair of zero words with another
complete sprite data structure, which describes the reuse of the DMA channel at a position
lower on the screen than the first use. You place the two all-zero words at the end, of the
data structure that contains the information for all usages of the DMA channel. For
example, Figure 4-10 shows the data structure that describes the picture above.
- Sprite Hardware 113 -
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