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.
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
