3rd party pci dma engine

Is it possible to create a 3rd party pci dma engine?

I would like to dma to/from host memory to a pci device that supports burst read/writes but has no dma hardware.

This mythical circuit would be saying "Hey! Mr Host please send a block of data to that pci device over there." or "Hey, Mr Host grab a block of data from that pci device and put it in your ram."


Reply to
Chad Bearden
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You would probably have to design hardware with master functionality to do this.

This could then grab the data in a burst from the source (as long as it's on the same local bus, I think there might be implications with crossing bridges) then burst write it to the destination.

Dependant on the amount of intormation to be transferred this double action would probably be faster than the host reading the info

4 bytes at a time.


------------------------------------------------ Nial Stewart Developments Ltd FPGA and High Speed Digital Design

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Reply to
Nial Stewart

You need a PCI master: each DMA operation reads (using PCI Master transactions) from a source device to a FIFO, then writes (again, using PCI Master transactions) to the destination. Both X and A have an FPGA PCI master/target core, but its NRE is not trivial; if your application is not intended for a large design, I'd recommend using and off-the-shelf PCI interface chip (PLX or similar) and an FPGA on its local-bus side. IIRC, the PLX chip even has an integrated DMA controller between the PCI and local bus, making the FPGA much simpler and smaller than if it had to contain a PCI core and a DMA controller.

Some additional issues: you need some sort of a DMA-Request signal (maybe use one of the INTx# lines and mask it for the CPU's int'pt controller?). The design would work better it you can distribute DMA cycles and not transfer everything in one huge burst.

And finally: why not change your I/O device to one that has PCI-master capabilities? if it's a third-party one, there are probably others with the same functionality; if it's your own design, you can re-design it - adding PCI Master capabilities at the source is much easier than adding it in an additional, dedicated card.

Reply to
Assaf Sarfati

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