[time-nuts] Question concerning failure and value of HP 5371A

Hal Murray hmurray at suespammers.org
Sat Oct 15 15:38:56 EDT 2005

> The point is, I do not find gates capable to work well beyond 30, 40
> MHz. I there somebody having a helpful idea how this could be solved? 

How fast do you want to go?  Modern FPGAs are loafing at 100 MHz.

A major problem at high speeds is signal integrity.  You can't toss something 
together with proto-board technology.  You need a good ground plane and power 
supply decoupling.  (and they generally require several power supplies)

If you want to get started with FPGAs, the Spartan-3 starter kit at $100 is a 
pretty good package.  You can get it from Xilinx or Digilent
It's got a 50 MHz osc.  (Beware, the connectors around the edge don't have 
enough ground pins for serious high speed work.)

Peter Alfke, chief apps wizard at Xilinx, has made a hobby out of using FPGAs 
for things like measuring pulse duration and/or frequency.  He's posted 
several neat ideas on comp.arc.fpga over the years.  They may be hard to find 
- "counter" is a popular term.

The latest trick that I remember is to use the high-speed SERDES logic on 
newer chips to sample a raw signal.  You get 20 bits in parallel with a 
sample rate of 2 GHz.  Then slower logic can count the transitions or 
  Message-ID: <BC8772E1.5C19%peter at xilinx.com>

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