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I am in the process of implementing a custom processor architecture into an FPGA, and once the design and burn-in is complete I want to test it by giving it simple commands via a built-in 8-bit parallel interface.

Obviously, I intend to write a program capable of instructing it on the PC side, with ideally every logic concept for the interface handled by the processor itself. That is, no support chips or architecture between the PC side and the parallel bus architecture on the chip.

Question is, is it possible to assert control over all pins of the parallel interface? Ideally, I would use the Acknowledge and Select pins to create a custom handshaking protocol between the test program and the chip - the combination of which of the two are tied high or low would determine the processor core's action on the data stream at pins D0-7.

I have read about commanding the parallel port using inpout32.dll, but does that allow "under-the-hood" access to all functions of the port or does it simply provide a means to use it to communicate, hiding all other functions or automating them?

I realize I could easily brute-force and implement a function into a microcontroller acting as a buffer - that is, USB transfer it the data and have it handle the logic implementation of the transfer throughput itself, but I would much rather have the interface controlled completely by the computer.

Ira Baxter
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ecfedele
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  • Do you have a PC that actually has a parallell interface? There not that many of them on the market these days. What is your FPGA? Xilinx or Altera or MicroSemi? Depends on what FPGA you have, you may have different options. – FarhadA Jul 22 '13 at 06:59
  • I have an old XP with a parallel interface on it. Sure, it's old, but most modern coding should still work on it. I can also get a parallel PCIe card for the desktop I'm using now. I'm using an Altera Cyclone III FPGA. – ecfedele Jul 23 '13 at 09:59
  • Check out this PDF file: http://www.xess.com/appnotes/an-111601-xsapport.pdf it has everything you need. – FarhadA Jul 23 '13 at 13:50

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