Apparatus for slave DMA emulation on a computer system bus

摘要

Apparatus for providing slave direct memory access (DMA) support on a computer system bus that does not support slave devices, such as the personal computer interconnect or "PCI" bus. An adapter card or microprocessor has a local DMA controller that can act as a busmaster and simulate a system DMA controller which would normally be used during slave DMA operations. Alternatively, the local DMA controller can work with an existing system DMA controller so that application software receives the correct status when polling registers in the system DMA controller. The local DMA controller allows the system DMA controller to operate as if the system DMA controller is controlling DMA transfers. In this way device contention between the system DMA controller and the local DMA controller is avoided.