Date   : Sun, 28 Aug 2005 15:09:59 +0100
From   : Phil Blundell <philb@...>
Subject: Re: 80186 co-pro

On Sun, 2005-08-28 at 13:52 +0100, Dr. David Alan Gilbert wrote:
> Aren't there some small logic level converter chips (basically a bunch
> of FETs) that are used for solving this type of stuff? I seem to remember
> they are typically 8 per chip.
> (Maxim seems to list zillions of similar types of things:
> http://para.maxim-ic.com/compare.asp?Fam=bidirtranslators&Tree=Interface&HP=Interface.cfm&ln
> )

Yeah, that's right.  It certainly isn't an insuperable problem; it's
just a bit of a nuisance to have to do that to all the signals.

The external tube interface also has the added complication that the
host and parasite might be powered independently, so the inputs mustn't
have any clamping diodes to Vcc.  The Spartan/XL I/Os meet that
requirement, but a lot of the level shifters don't.

p.