Wire-wrap and low cost TTL parts have made the puzzle-solving
fun of digital logic design accessible to hobbyists and engineers
everywhere. Although TTL works fine for small designs, it becomes
expensive and time consuming for larger designs. Field Programmable
Gate Arrays (FPGAs) contain thousands or millions of uncommited
gates and are almost ideal for large designs. The problem with FPGAs
is that you have to learn a design language (Verilog or VHDL) and that
in order to write even simple Verilog programs you need to set up a
fairly complex development environment. It is the latter problem —
the development environment — that this article addresses.
By Bob Smith
Iinstall the Xilinx FPGA design
tools, how to use the Xilinx
n this article, you'll see how to
command line tools to compile a
Verilog or VHDL design, how to
download the compiled code to
an FPGA board, and how to
automate the whole process using
a “makefile.”
The Xilinx command line tools
are the same for both Linux and
Windows, making this article useful
for almost anyone with a computer
(including Mac users using a Linux
virtual machine). The sample design
for this article is a 28 bit counter
which has the most significant
eight bits visible on LEDs. It is
counting transitions on a 12. 5 MHz
clock giving the least significant LED
a flash rate of about 6 Hz. The
circuit has a counter reset line tied
to a button.
The hardware used herein is the
Demand Peripherals Baseboard-2
which has a Xilinx Spartan-3E, LEDs,
buttons, and a USB interface for
downloads and user data. Since the
Baseboard-2 is downloaded through
a USB serial port, it doesn't require
the expense and complexity of a
separate JTAG dongle or the hassle of
installing JTAG drivers — and not
requiring them is particularly nice for
Linux developers. (I helped design
the Baseboard-2 and one of our
major design goals was to allow USB
serial downloads.)
Installing the Xilinx
WebPACK Toolkit
Xilinx provides a set of free
design tools, the WebPACK, that runs
on both Windows and Linux. Xilinx
supports the tools on Windows XP
Professional and on recent versions
of Red Hat Enterprise Linux and SUSE
Linux. While not officially supported,
WebPACK runs fine on XP Home
Edition, Vista, and Ubuntu. To get the
tools working on your system, you
have to go through about a dozen
web pages to start the WebPACK
download, wait for a 2.2 GB
download, and then go through
another dozen or so screens for
the installation. It is tedious, but
straightforward.
Start by going to the Xilinx
download site at:
www.xilinx.com/
support/download/ index.htm. Skip
the Search button and scroll directly
down to click on the "Download ISE
WebPACK" link. This will take you to
a login page where you can select
"Create Account" (since you probably
don't already have a Xilinx account).
You will receive an email message
with a web link where you can go
to finish the registration and to log in.
After logging in for the first time,
you're asked to provide more
information. The Next button will
take you to a screen that displays
what Xilinx packages you are
entitled to download. Select ISE
WebPack10.1 and click on the
Next button.
The next page — the Product
Registration and Download page —
February 2009 49