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Message
From: Rudolf Usselmann<rudi@a...>
Date: Sun Dec 28 18:40:54 CET 2003
Subject: [oc] Newbie FPGA question
On Sun, 2003-12-28 at 23:55, Fabrizio Fazzino wrote:
> Hi guys,
> I'm new to the FPGA world (I've been ASIC verifier for
> some years but I've left the company and now I do not
> work anymore in the electronics field) and I would like
> to have an idea of the budget required to test my own
> projects on FPGA.
Welcome to the mess of FPGAs !
> I suspect that first of all you'll ask me how many
> gates and I/O ports I need; let's say I'd like to try
> an nnARM core + some peripherals (DMAC, PWM, RTC and
> SRAM memory interface); You know better than me whether
> this SoC requires thousands or million gates.
> I would be happy with lower performances if this
> ensures lower costs: just let the design fit into the
> die.
My EWAG would be Spartan 2 300, PQFP 208 or even maybe
a PLC 144 package.
Remember the gate count the FPGA bozzos give you is at
best 1/8 of real ASIC/full custom gates. So a 300K
Gates FPAG, is about 38K gates in the "real world".
Sometimes I wonder what kind of grass the FPGA guys
are smocking - I'd like to get a hold of some of their
weed, seems to be very delusional ... ;*)
> Then, these are some newbie questions whose answers
> will help other people in the same situation:
> 1) how much does (approx) the "FPGA programmer" cost?
All you really need is a Parallel Cable 4 from Xilinx,
about $100 USD. I suppose you can use it with the Free
Web Pack, but you better make sure - I just found out
that Xilinx commercial release if the ISE 6.1 for Linux
does NOT support the Parallel Cable 4 - dhuuu, never buy
the SW and HW from the same FPGA vendor ...
I too came from an ASIC and full custom life to FPGAs,
and have never encountered such mess with an ASIC or
full custom flow. FPGA flow reminds me of Vegas ...
> 2) what is its aspect? is it "huge" or just like an
> external modem with one socket?
Not sure what you mean, an FPGA, is a standard chip, in
whatever package you chose, you will also need a PROM to
hold the configuration of the FPGA. That can be a real
PROM or a flash/ee based ISP PROM.
> 3) how much does the single programmable unit cost?
I believe the Spartan 2 300 are in the $30 USD range ...
Remember you also need a PROM. You can program the FPGA
directly from the parallel cable 4 without a PROM, but
once you turn off the power the configuration is gone.
This is however very useful for initial debugging.
> 4) are the units programmable more than once?
Depends on the type of PROM you get.
> 5) from this user perspective, is there any difference
> between an FPGA and a PLD?
Yes ! A huge difference. Think of an FPGA as a really
limited Gate Array. Some special operations have dedicated
support inside most FPGAs (such as memories and shift
registers, and in some even multipliers).
> 6) do I need a strong competence in analog electronics
> to build up the development board or is there any
> standard board I can use with default allocation
> of the pins (e.g. to access the onboard memory)?
Not really. Depending on the speed of your design you
have to pay attention to the obvious signal integrity
issues. Other than that, pay close attention how you
power up the FPGA, they have some special requirements
that are easily solved by studying several app notes ...
If you are just "playing around" it might be cheaper to
just buy a development board. If you have a specific
project in mind and require some special interfaces/chips/
PHYs, you might have to build your own. But, check around,
you might find a development board that has what you need ...
> Sorry for these questions but I have looked over the
> web and have found only tons of advertisement.
>
> Thank you very much in advance,
> Fabrizio
Good Luck !
Regards,
rudi
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