Path: utzoo!attcan!uunet!zephyr.ens.tek.com!gvgpsa!gold!grege
From: grege@gold.GVG.TEK.COM (Greg Ebert)
Newsgroups: sci.electronics
Subject: Re: Termination of TTL <-> TTL cable
Message-ID: <1215@gold.GVG.TEK.COM>
Date: 30 Jul 90 19:39:01 GMT
References: <26b48046.147d@petunia.CalPoly.EDU>
Distribution: na
Organization: Grass Valley Group, Grass Valley, CA
Lines: 12

In article <26b48046.147d@petunia.CalPoly.EDU> jburch@polyslo.CalPoly.EDU (Jerry Burch) writes:
>
>
>I am working on a project which needs to communicate over a ten foot cable
>with TTL gates on either end. 

This one is 'compliments of the floppy drive manufacturers'. First, you
alternate signal and ground lines (odd=GND/even=signal). Signals are driven
by open-collector drivers, such as the 74XX38. At the other end of the cable,
you pull-up  w/150 ohms. If you parallel 2 drivers, you can terminate the
line closer to its characteristic impedance, which is somewhere between 50
and 100 ohms; use a TDR scope and experiment.