PLDs and development software

[Steven Curtin]

>The big difference that applies to DIY'ers is the fact that Xilinx (and
>some other) FPGAs are configured at power-on with "bitstream" data. Thus,
>if your project has a microcontroller CPU in it already, you can merge the
>bitstream with your code, and have the CPU configure your hardware in the
>FPGA. PLDs are typically programmed in a device programmer. These used to
>be extremely expensive, but now you can find some with a limited set of
>supported devices for a few hundred dollars. Still, it is an expense you
>don't have with Xilinx FPGAs. 

This is one big advantage that the Philips xPLDs have over other PLDs, in
that they're based on Flash memory.  This means that you can download the
PLD data over a ribbon cable that goes between the PLD's JTAG port and your
PC's parallel port with no external programmer required.  The data stays
intact in the part when power is removed so you can take it out in the
field without having to take your PC along.  With Xilinx you have to either
attach a microcontroller or serial EPROM to program the part every time you
power up, with many PLDs they're one-time-programmable so you have to throw
away an expensive part if you make a mistake or want to change something.
I'm going to get some experience in XPL before diving into VHDL myself-
thanks for the sites, it's great to know there's affordable VHDL compilers
out there, even if they're tied to one chip.

Steve C



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Steven Curtin  
http://www.emf.org/people_curtin.html
Lucent Technologies - Bell Labs Innovations
rm. 3C-208, 200 Laurel Ave S
Middletown, NJ 07748-4801  U S A
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