ISA DMA: Difference between revisions
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ISA DMA
The idea behind DMA is that you can set up a 'channel' with an address pointing into memory and the length of the data to be transferred. Once set up, you can tell the peripheral owning the 'channel' to do whatever it is supposed to do (e.g. read a sector). Then the CPU can go onto something else. Periodically when the data bus isn't being used by the CPU the DMA chip takes over and transfers data between the peripheral and memory without involving the CPU. When the transfer is complete (e.g. an entire sector has been sent to the floppy drive) the DMA chip will than signal that it is finished. The DMA chip can even signal if it has run out of data, allowing the CPU to program some new information and another transaction to proceed.
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