kc5tja wrote:
ElEctric_EyE wrote:
Virtex 2 would probably be a nice choice for a 6502 on FPGA, since no logic level converters are needed... Although, I can't find any!
This is the problem with the FPGA industry as a whole. Once an FPGA becomes cheap enough to fall into amateur hands, they discontinue the architecture, we're forced to grovel for scraps. It wouldn't be so bad, though, if FPGA vendors would agree on a wire standard for programming not only current devices but future devices as well. But, no, they can't let out any "trade secrets."
You can pick up a Virtex II at digikey for about $80 for the smallest chip. Thats not bad for a Virtex - you're really looking at the wrong family; the VIIs are approaching discontinuation and are old devices. They're really intended for building high performance, low quantity, high cost equipment - think network switches and such. The more expensive ones (Up to $4000 per chip) are generally rarely found outside development boards (They're often used for CPU design).
If you want an FPGA family to use for your own designs, look at the Spartan III (or Altera's alternative). They're the volume families, built in more modern processes and cheaper to produce. Of course, they don't have 5V IO - the process nodes which support them economically simply can't support it.
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This is why I support Intellasys and GreenArrays chips so much. I really hope they can bring chips to the mass market, so that we can hack with general purpose, long-lived hardware instead of the poster-children of planned obsolescence.
Planned obsolecesence? The Virtex II family is over 10 years old. That's a very good life span for a device of this complexity. Processes get discontinued, and Xilinx aren't at liberty to choose when (no fabless company is).
Oh, and the programming information for Xilinx devices is very well documented. The open source OpenOCD JTAG system knows how to program them; as does the free ISE software.
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Yes, while slower than FPGAs, they're plenty fast enough to drive a VGA entirely in software at 640x480, if not 800x600 with tricky programming.
Tell me: If I program that for a GreenArrays device, how do I move it to one by another vendor?
Because, with an FPGA, all I do is recompile it with their software. The language is standard. Heck; most of the time even the programming cables are standard (and, indeed, via OpenOCD you can use the same cable to program your FPGAs, CPLDs and ARM CPUs - and all through the same board connector)