Re: CPLD and FPGA designs

From: Brad Eckert (nospaambrad1_at_tinyboot.com)
Date: 03/08/04 

Date: 8 Mar 2004 13:15:56 -0800

Rene Tschaggelar <none@none.net> wrote in message news:<4049dd26$0$710$5402220f@news.sunrise.ch>...
> Scott McDonnell wrote:
> >
> > Sorry if these questions seem like newbie questions, but I have found tons
> > of resources on HDL programming, but very little on actually going from
> > software to hardware.
>
> You must not compare CPLD and PFGAs by the need of an external
> storage. CPLDs have up too 512 FlipFlop Macrocells, wheras the
> FPGAs have thousends to millions of Flipflop macrocells.
> The CPLDs have their own EEPROM onboard, while the FPGAs need
> something external. This allows you to (re)load the FPGA from a
> processor.

You'll find that out soon enough when you try to fit your design in a
CPLD. If you're trying to stick to instant-on operation and one power
supply and the design still doesn't fit in a CPLD that you're willing
to pay for, you could try an antifuse based FPGA from Quicklogic or
Actel.

When you write your HDL, keep in mind that you're describing hardware
not writing software. The code you write fills out a huge logic graph
that gets reduced by the synthesis tool. If you do something wrong
some of your circuits get reduced to nothing, so fitting the design
before you've debugged it with a simulator might give overly
optimistic results. 

--
Brad Eckert

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