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RS-485 P2-550 to Sureservo SVA-2040

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  • RS-485 P2-550 to Sureservo SVA-2040

    This is just a question about proper use of the termination resistor that the documentation mentions. I am using the RS-485 terminal block and wiring a Ziplink ZL-ZDM-RJ12X4 module. Then four connecting cables to 4 sureservo drives. I am using about 12 inches of Belden cable from the RS-485 port to the ZZL-ZDM module. I did not put a terminating resistor anywhere when I tested this and had no communication issues that I could see. I installed everything into its enclosure and still have no issues. However, as I was reviewing everything I decided to place the 120 ohm termination resistor on the terminal block of the CPU. Everything is still working good.
    Here is the question, do I need to install another resistor on the Ziplink module terminals? Is the single resistor OK?
    I should point out, that I am not really checking for communication failures in the PLC logic. I rely on the servo drive to fault when it detects failed communications (set the time out value parameter). However, I have never had this alarm code (ALE20) appear unless I purposely unplug the communication cable to that specific drive.
    Forgot to mention, should I ground the shield wire? As of right now I just left it. I feel the run is so short that it makes no difference.


  • #2
    Just a bump, anyone have an opinion about my use/no use of the termination resistors?

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    • #3
      Originally posted by LesKlar View Post
      Just a bump, anyone have an opinion about my use/no use of the termination resistors?
      short wiring - shielded wiring - daisy chain - low to mid baud - low node count -- probably not required
      other configs -- use the term resistors

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