5/18/2017 12:42 PM | |
Joined: 9/27/2006 Last visit: 8/22/2024 Posts: 12279 Rating:
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Hello GUWS; The terminating resistor on a RS-422/RS-485 bus is designed to match the impedance of the line (analyzed as a transmission line) to the impedance of the last and first nodes on thre bus. You remember that matxched impedance on a power circuit allows maximum power transmission, and on transmission lines it eliminates signal reflections and VSWR. There are a great many technical explanations to be found on the web, please look at this one as an example: RS485 & RS422 - When is termination required? The "range" of the résistors is purely local. It acts on both extremities of the bus (first and last node); if you activate a termination resistance on another node, this one becomes the last node of the bus and you lose communications with the nodes past it. I have the feeling that this was not the answer you were looking for; in that case, review your original question and change the phrasing to reflect your query better. Hope this helps, Daniel Chartier |
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