Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!rutgers!cbmvax!daveh
From: daveh@cbmvax.UUCP (Dave Haynie)
Newsgroups: comp.sys.amiga.tech
Subject: Re: Bus Termination
Message-ID: <6841@cbmvax.UUCP>
Date: 11 May 89 21:21:53 GMT
References: <2487@csd4.milw.wisc.edu>
Organization: Commodore Technology, West Chester, PA
Lines: 31

in article <2487@csd4.milw.wisc.edu>, trantow@csd4.milw.wisc.edu (Jerry J Trantow) says:
> Summary: What's the Scoop

> Line Eater fodder

> The fix that has been suggested uses a 1K,4.7K, and 0.001 uF....
> To clear up the confusion, I dug up my A1000 schematics.  The expansion board
> that is shown in the schematics shows a 220 and 330 ohm bus termination ...

> So what is the scoop.  Is the capacitor really needed?  Should I put Rs on
> the address, data, and control lines?

The resistive termination is appropriate for an expansion bus with good, 
strong bus drivers, like the 74F245s recommended for that Los Gatos backplane
design.  What you're talking about is sitting on the Amiga's local bus.  I
doubt that the local bus will be able to drive such termination.  The R-C
termination that's been suggested for LUCAS is probably best.  Not only is
it mild enough to let the rest of the system keep working, but there's a good
chance that it's tuned to the particular interface problems that exist
beween LUCAS and the A1000.  If you know the exact situation you're trying
to supply termination for, you can do an application specific job.  If you're
trying instead to terminate an "anything goes here" thing, like an expansion
bus, you do things a little differently.




-- 
Dave Haynie  "The 32 Bit Guy"     Commodore-Amiga  "The Crew That Never Rests"
   {uunet|pyramid|rutgers}!cbmvax!daveh      PLINK: D-DAVE H     BIX: hazy
              Amiga -- It's not just a job, it's an obsession