Re: gEDA-user: Spartan3 FT256 layout in PCB

[Greg Bengeult <gregbengeult@xxxxxxxxxxx>]

Larry Doolittle wrote:

> Unlike previous generations of Xilinx chips, I couldn't find any
> recommendations/app notes for decoupling of the Spartan3.  So I
> don't know how many decoupling caps to attempt, beyond the obvious
> "one per power pin".

Xilinx has an app note on their web site (XAPP623) that addresses the 
decoupling issue for any chip, not a specific type or package.  It's 
written for engineers and can be a long and dry read, but all of the 
important information is in there.  Take a look at
http://direct.xilinx.com/bvdocs/appnotes/xapp623.pdf

HTH,
Greg Bengeult