Tim's own version of the Catweasel/Compaticard/whatever

From: Chuck McManis <cmcmanis_at_mcmanis.com>
Date: Tue Jul 4 20:34:54 2000

At 06:11 PM 7/4/00 -0700, someone wrote:
> > The CPLD offers a number of advantages over FPGA's. They're not the same.
> > An FPGA uses a RAM lookup table in to define the function executed by a
> > logic cell. CPLD's use EPROM/EEPROM cells to store the logic
> configuration.
> > Most FPGA's require an external configuration prom of one sort or another,
> > which it boots on reset.

Not all FPGAs use RAM, infact it is one of the suggested advantages of
Xilinx FPGAs but it isn't a requirement. CPLDs generally have simpler
configuration blocks (or macrocells, or what ever the manufacturer wants to
call them)

>Actually it's pretty easy to get an Xylinx FPGA to read a program from a
>serial or parallel line, so all you need to do to reprogram is assert reset
>and feed in the data correctly.

This is true and the ultimate "catweasal" type board would have a nice fat
ram loaded FPGA connected to the interface logic and a high speed ram
buffer. Probably a programmable clock too. That way you could run anything
from an actual WD1793 type chip to an HP logic analyzer just by downloading
a different setup.

--Chuck
Received on Tue Jul 04 2000 - 20:34:54 BST