Abstract: A semiconductor device with an embedded PCI 2.1 compliant bridge provides expanded functionality as system-level implementations of a PCI-to-PCI bridge, and enhances the level of integration possible. The embedded PCI-to-PCI bridge allows the creation of multi-function, multimedia add-on cards supporting multiple devices. Multi-function, multimedia subsystems that provide audio, graphics, MPEG, etc., are mapped into a bridged-to PCI-bus that keeps such traffic off the main PCI-bus. The advantage for the system or add-in card vendor is that the various multimedia chips that are combined can come from different sources, providing an optimized and highly customized combination of functions.

Abstract: A transparent direct memory access method comprises emulating an ISA-bus mapped direct memory access controller (ISA-DMAC) with a PCI-bus mapped direct memory access controller (PCI-DMAC). The ISA-DMAC exists, but there may not actually be any resources mapped into the ISA-bus space. Write snooping by the PCI-DMAC of a PCI-bus processor detects whenever an attempt is made to write the ISA-DMAC, and copies the data written into the ISA-DMAC registers into a corresponding register of the PCI-DMAC. The direct memory access operation commanded by the PCI-bus processor of the ISA-DMAC is performed by the PCI-DMAC in the PCI-bus resource space. When the direct memory access operation is completed, the PCI-DMAC updates its registers and does a write back to update the ISA-DMAC registers. The PCI-bus processor can then read the PCI-DMAC directly for status, or if legacy software is running the ISA-DMAC will respond with the appropriate register value.