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Guest jackson

DH485 network

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I'm curious...can't you simply wire 5 SLC 5/04's together with a RS485 rated cable on a DH485 network? You don't need to use AIC's, correct? And if this is true, do you just wire all the transmit enable signals together? Does anybody know what that pin is for?

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jackson, fixed SLC 500, 5/02, and 5/03 use DH-485 which require the use of the 1747-AIC. SLC 5/04 use DH+ and DF1 (RS232) for communication. With the DH+ you can connect the processors together with the "Blue Hose" (1770-CD). Set each one up as a seperate node. You can use the MSG instruction to talk to each other.

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Purchase Belden #9463, it's cheaper than AB 1770-CD (They are the same cable)

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Oops...I actually meant SLC 5/03.... Thanks for the replies...So it is absolutely necessary to use an AIC for the DH485??? Seems strange for a RS485 network.... Thanks again...

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Oh, no, you're perfectly free to wire together the RJ45 jacks in a nonisolated daisy-chain. Just make sure that you can prove your ground planes at each controller are all grounded to a noiseless common bus. The AIC's are for isolation, so that it doesn't matter what ground potential the SLC controller is wired to. Pretty handy if your factory has more than one building or power source. Why didn't A-B just put an isolated port on the SLC in the first place ? The answer is lost to the mists of time. The AIC's also have something to do with powering ports on things like the 1747-PIC. Check out the excellent tutorials at www.robustdc.com. Those guys taught me a lot about communication networking... and showed me how little I really knew.

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Excellent. Makes perfect sense. That brings me back to my original question....the transmit enable pin. Can I just ignore this for a straight RS485 wiring network? Is it only used for the AIC? Or do I need to have it wired to something? I can, of course, just try it to see if it works, but it's nice to know this up front when building the cable. Thanks.

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