PLDs and development software

[Tim Godfrey]

For those interested in using PLDs and FPGAs for DIY projects, there are
many differences between PLDs and FPGA devices. The architectural
differences between PLDs and FPGAs tend to make one or the other better for
a given application. 

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. 

If your application doesn't use a CPU, Xilinx parts can be self-configured
using serial or parallel EE or EPROM.

Xilinx often has specials on their development tools. Currently they have a
development system for $99, It has a non-standard HDL (Abel HDL), but it
does not include VHDL, or support for the larger (above 20K gates) devices.
See http://www.xilinx.com/products/software/found/baseblst/valpromo.htm> 

If you prefer PLD devices, Cypress offers their "Warp 2" VHDL compiler (for
their parts only) for $99.  See
<http://www.cypress.com/cypress/prodgate/tool/overview.html>

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