Basics FPGA

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Hi Everyone,
I am an electrical engineer but I have never had a chance to learn
about FPGAs. I think now is a time to make a foray in this world. My
problem is I dont know where to start. So I will appreciate if someone
can tell me what are the things I will need to start from scratch, like
software, hardware etc. Thanks a lot


Re: Basics FPGA
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You can't go wrong with the $99 Xilinx Spartan 3 kit and free WebPack
software. I actually got my kit from Digilent who make them for Xilinx and
paid an extra $20 for the larger -400 Spartan 3 chip.

Leon



Re: Basics FPGA
Hey Leon
Thanks for the reply. I think I also emailed you directly using my
other ID for a private tution on FPGAs. Let me know if you can do that.


Re: Basics FPGA
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There are two main flavors of HDL for programming FPGAs, Verilog or
VHDL. You could try Verilog first, since it has a lot of free tools
available, including free compilers and simulation tools.

GPL Cver (a free verilog compiler): http://www.pragmatic-c.com/gpl-cver /
GTKWave (free waveform viewer for GTK):
http://www.geda.seul.org/tools/gtkwave /

With the above two free tools you could learn how to program in Verilog.
Then you can move on to commercial tools such as Xilinx's ISE and EDK to
do real FPGA synthesis.

Good luck!

Re: Basics FPGA
Thanks for the info. But I had a question and pardon my ignorance here.
Some one also suggested that I buy Xilinx Spartan 3 kit and free
WebPack
software. What is the use of that? Is that used to actually program
FPGA chip? As far as I understand i can use the tools you suggested to
practise simulations and then go towards the hardware to program the
chips.


Re: Basics FPGA
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The Spartan 3 kit comes with a prototyping board with a Spartan 3 FPGA.
The software that comes with the kit lets you synthesize your design
into the FPGA on the board. You should definitely get something like
that if you want to get a feel of what the logic you wrote can do in
real hardware.

And you are right, you can practice with simulation tools first (this
lets you see the inner-workings of your design, not just the output).

Re: Basics FPGA


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Blinking leds and displaying stupid messages on the 7-segment things
is more fun than reading pages of $monitor() outputs !

MB


--
Michel BILLAUD                   snipped-for-privacy@labri.fr
LABRI-Université Bordeaux I     tel 05 4000 6922 / 05 5684 5792
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Re: Basics FPGA
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Reading a waveform of 100Hz is easier on your eye than LEDs blinking 100
times a second.

Re: Basics FPGA
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The steps are

Create the design:

1) edit design source files
2) create test bench files - these files simulate other parts of the
system your FPGA goes in, provide stimulus. For trivial designs, the you
might get away without testbench and just use the simulator to apply
stimulus.
3) simulate your design in the testbench environment. Go back to step 1
until it appears to work right. The simulator is seldom provided for
free by the fpga vendor, although xilinx supplies a free but hobbled
version of modelsim, which is very good.

4) use a logic synthesizer to convert your design source files into a
structural/schematic implementation of the logic. This tool is usually
supplied by the vendor, but sometimes 3rd party tools are even better.
5) use place and route tools to map the schematic onto the cells of a
particular fpga. Timing constraints tell the tool how fast your design
must be. This tool is always supplied by the fpga vendor.
6) after verifying that timing constraints were met, load the results of
5 into the fpga, watch the blinkenlights.

Most fpga vendors provide free gui type programs that tie all these
things together. You can run all the tools from command line also. I
prefer doing steps 1-3 "stand alone".

There are some cases where simulation is called for after step 4 and 5,
but that is rare for simpler designs.

Re: Basics FPGA
You can go through this very good introductory tutorial on PLDs/FPGAs.

http://klabs.org/richcontent/Tutorial/fpga/Toronto_tutorial.pdf


Re: Basics FPGA
Thanks for the response. I have already come across that article. What
I am looking for is how do I start working on it once i figure out the
basics. For example to learn C++ i need C++ tutorials, a C compiler and
a computer. similarly what all is required to get started on this. Also
what all can I get for free. Will Hua Zheng suggested some simulation
tools to learn verilog. Do I also need any hardware? thanks


Re: Basics FPGA
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You only need an editor and simulator to get started.
Once you know how to write and simulate HDL code for
synthesis, you can try it out on hardware.
Until then, all you can do with hardware
is run the canned demos and flash the LEDs.

           -- Mike Treseler

Re: Basics FPGA
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You don't need hardware to learn HDL. Cver + GTKWave will simulate most
logic.

Re: Basics FPGA
Hey,

     First start writing small designs and try to simulate and verify
them using some free simulations tools in the web. Xilin also offering
some evaluation versions of simulation tools. Then you should
synthesize your and design followed by place & route and Static timing
analsys (STA). Then you require hardware to actually verify your design
in FPGA. Until STA you can manage with free web tools but to test your
design in FPGA you need hardware and no company is provinding hardware
for free.

--Joe


Re: Basics FPGA
Also, get "Design Warrior's Guide to FPGA" - a very good intro to the
technology, workflow etc.
There's probably 6-9 good books on Verilog and VHDL - for quick start
get something tailored toward
practical world design of synthesizable logic.

Here's another excellent site: http://www.fpga4fun.com . 30 mins of
browsing through it will tell you
85% of what you need to know about FPGAs


Re: Basics FPGA
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Since the other posts concentrate on Verilog, I'll give you some
pointers on VHDL. Don't want to start up the old Verilog vs. VHDL
discussion, just want to give you both options. Since I don't know
Verilog, I can't comment on what is easier to learn if you're just
getting started.

There's a VHDL-tutorial on http://www.vhdl-online.de (available in
English), which is OK for starters, I think. On
http://www.amontec.com/fix/vhdl_memo/index.html you can find an on-line
syntax reference, which is pretty handy.

As editor for your source files I recommend Xemacs (
http://www.xemacs.org ), which has excellent support for syntax
highlighting, TAB-completion, easy generation of the most commont VHDL
constructs and so on, and of course it's free (BTW, it supports Verilog
as well).

For simulation, just download Xilinx' free ISE WebPack from
http://tinyurl.com/bk7km , which includes a limited release of ModelSim
(I think it's restricted in simulation speed and the number of lines
your source files can have, but it should be enough to get you started).

Should you decide to go into this area of work, ModelSim is very likely
to be the simulation tool you'll be using, so you might as well just
learn the ropes with that instead of starting with another tool and then
having to switch to ModelSim later (BTW, WebPack as well as ModelSim
support both Verilog and VHDL).

ISE WebPack also includes a tool for synthesis, which I think is a good
thing for people starting out with the whole FPGA thing. I find that
especially for people coming from a software background, it's good if
they see from the beginning how their coding style affects the hardware
that is generated.

Simulating everything until it does what it's supposed to do is one
thing, but sooner or later you also have to develop a feeling for how
the tools map your code to the hardware.

So I think it's not a bad idea to just run synthesis on your code and
have a look at the schematic it generates from time to time. As long as
it's a smaller project and not too complicated, that can teach you a
thing or two as well.

Another thing the others haven't mentioned is the fact that you can work
with FPGAs without using a HDL at all. Smaller, simpler projects can be
entered through schematic entry. This gives you the most control of what
will end up in hardware, but can of course get very tedious...

HTH,
Sean

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