adccommunitymod (AutomationDirect) asked a question.
Created Date: April 21,2007
Created By: a agnone
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Can someone please sort it out for me. The more I read the forum under this subject, the more confused it sounds. I am not sure if I want to use a DL250-1 or DL260. The setup is 2 servos, SVAV2040, connected to a DL250-1 or DL260. Pages 7-8 and 7-9 in the servo manual show the wiring. Since I am not sure what CPU I will use, can I use RS232, it seems to work on both with the same cord? Then there is RS422 on page 7-9 works on both. What about RS485, only works on DL260. I read somewhere that the difference between RS485 and RS422 was one was not multidrop and could not communicate both ways. The real questions is should I just wire two cables (SVC-MDCOM-CBL), in parallel and use the RS-422 config and all will be okay? I was also told that since in the same cabinet, inches away, I do not need the resistors.
Created Date: April 21,2007
Created by: KPrice
I can offer some basics. RS232 is only point-to-point, only (2) devices can communicate. Both RS422 and RS485 can be multi-dropped in daisy-chain configuration, (2) or more devices can communicate. In daisy-chain, the cable goes from the first device, then to the next, then to the next, etc. The RS422 must be "4-wire ", actually requires requires (5) conductors, and can have up to 10 drops. RS485 can be 4-wire or 2-wire (3-conductors) and can have up to 32 drops. The RS485 2-wire is either transmitting or receiving since transmitting and receiving are on the same pair. You are correct that for short cable runs and lower comm rates you do not need the termination resistors. B&B Electronics www.bb-elec.com has very good application notes on RS232, RS422, and RS485. Hope this helps.
Created Date: April 21,2007
Created by: a agnone
Can someone please sort it out for me. The more I read the forum under this subject, the more confused it sounds. I am not sure if I want to use a DL250-1 or DL260. The setup is 2 servos, SVAV2040, connected to a DL250-1 or DL260. Pages 7-8 and 7-9 in the servo manual show the wiring. Since I am not sure what CPU I will use, can I use RS232, it seems to work on both with the same cord? Then there is RS422 on page 7-9 works on both. What about RS485, only works on DL260. I read somewhere that the difference between RS485 and RS422 was one was not multidrop and could not communicate both ways. The real questions is should I just wire two cables (SVC-MDCOM-CBL), in parallel and use the RS-422 config and all will be okay? I was also told that since in the same cabinet, inches away, I do not need the resistors.