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Direct Memory Access

IP.com Disclosure Number: IPCOM000040402D
Original Publication Date: 1987-Nov-01
Included in the Prior Art Database: 2005-Feb-02

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Irwin, JW [+details]


A method is described which adapts the direct memory access (DMA) facilities on an integrated support chip for use on a coprocessor. This method allows the master processor of the IBM RC-RT to manipulate the coprocessor environment through registers on the coprocessor card. In addition, this method requires that the usual active DMA Acknowledge drivers on the planar be replaced with gated drivers so that the coprocessor can control the acknowledge lines for the appropriate DMA channels. Software running in the master processor insures that DMA channel assignment is exclusive. Optionally, attempts by the coprocessor to use unassigned channels may be detected by the master processor and the user informed.