On Friday 01 April 2016 13:58:55 Stephen Dubovsky wrote: > You can not include the termination or pull up/down resistors on a > RS422/485 network in the drivers (unless they can by disabled.) You > don't know where (or how many) are located on the bus. They are > multi-drop networks after all. Only terminate the two far ends. > Thank you Stephen, I hadn't remembered that as I only had one instance of it, point to point at the tv station, and it Just Worked(TM).
Can I blame it on aged wet ram? You are of course correct. > > On Fri, Apr 1, 2016 at 1:37 PM, Nicklas Karlsson < > > [email protected]> wrote: > > > > > Twisted pair is a transmission line and subject to all the > > > > > vagaries of load matching and such. > > > > > > > > > > That cables impedance is not listed there, > > > > > > > > Yes it is. 120 Ohms. > > > > > > Resistance is NOT impedance, Andy. And I first read that as 1200 > > > because my screen is high res and the ohm sign looks like another > > > 0 at first glance, I mentaly threw that whole line out as being > > > technically impractical, written by someone who obviously did not > > > understand anything about transmission line theory. My bad for > > > the miss read of 120 ohms as 1200 ohms, but still the use of the > > > word resistance renders it null and void in my technical mind. If > > > they meant impedance, they should have written impedance. If the > > > loads J dactor is 0, then they would directly correspond, but that > > > J=0 generally would be quite rare in the real world. > > > > > > However, my comments about the load termination, in this case with > > > a 120 ohm resistor from wire to wire at the load end are still > > > valid. > > > > https://www.expertdaq.com/static/img/info/RS485-termination-120-ohm. > >gif > > > > I think the extra bias network to power rails is necessary to get > > correct level in between data is sent. > > > > > Properly done, thats taken care of in the rs485 interface in the > > > device, but you never know when some bean counter between the > > > engineer and the production line will delete that seemingly > > > useless part as a cost saver. > > > > They save beans in the short but have to spend more of them later. > > By investing the beans in rather good fast growing soil they figured > > out they could return more of them later but still have some left > > for them self. > > > > > > -------------------------------------------------------------------- > >---------- Transform Data into Opportunity. > > Accelerate data analysis in your applications with > > Intel Data Analytics Acceleration Library. > > Click to learn more. > > http://pubads.g.doubleclick.net/gampad/clk?id=278785471&iu=/4140 > > _______________________________________________ > > Emc-users mailing list > > [email protected] > > https://lists.sourceforge.net/lists/listinfo/emc-users > > ---------------------------------------------------------------------- >-------- Transform Data into Opportunity. > Accelerate data analysis in your applications with > Intel Data Analytics Acceleration Library. > Click to learn more. > http://pubads.g.doubleclick.net/gampad/clk?id=278785471&iu=/4140 > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) Genes Web page <http://geneslinuxbox.net:6309/gene> ------------------------------------------------------------------------------ Transform Data into Opportunity. Accelerate data analysis in your applications with Intel Data Analytics Acceleration Library. Click to learn more. http://pubads.g.doubleclick.net/gampad/clk?id=278785471&iu=/4140 _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
