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METSYSTEM

RSLinx Comm Error On Eth-485 Gateway

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Evening all, I have an interesting issue with RSLinx. Currently upgrading an old windows NT SCADA server to a new Server 2008R2 system. The old Windows NT server has an older RSLinx version installed and communicates to the PLC network via an RS-232 - DF1 Devices driver, configured as 1770-KF3/1747-KE. It uses the old 'big grey interface box' (part number not known), that, I assume, converts the RS232 from the PC to the RS485 for the PLC's, this system works just fine, all PLC's communicating nicely in Linx. The issue I now face is that the new 2008R2 server is a new Dell R320 and has to connect via Ethernet. I have installed a CLX gateway with Ethernet card and 485 card and have linked to the PLC network via the AIC Link coupler. The problem I seem to be facing is the PLC's appear in the driver hierarchical tree but only stay healthy for 1-2 secs at a time. Most of the time they just have Comm error 00000020 and my system cant see them. I'm lost now, I have spoken with Rockwell and they cant understand it either?? The legacy network operates fine, the new system is setup as per manufacturers recommendations, and every now and again, I can see the PLC's, they just don't stay active for very long. Is the Ethernet card forcing the 485 network to poll faster than its capable?? See attached screen shot Any advice on this would be greatly appreciated Many thanks

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Is the "Old Grey Box" that you mention still connected to the network when you test with the new card? If it is, I would guess that it has the same node address as your 1756-DH485 card. Try changing the node address on your DH485 card to something like 10. If you can, disconnect the old interface and see if your problems go away. If that isn't the problem, let us know.

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Hey thanks, no the box has been removed and the new card has definitely got a unique node id. There are 6 PLCs numbered 1-6 and the card is numbered 0, I have also tried it as 10

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The gray box was probably a 1770-KF3, which translated DF1 protocol on RS-232 to DH-485 protocol on RS-485. The old DF1 connection via an RS-232 serial port to the old NT server gave the network bridge about the same amount of bandwidth on both sides. The DF1 link ran at 19200 baud, and the DH485 network ran at 19200 baud, but had to handle more token passing network timing. Now that you have 100 Mb/s Ethernet on one side, it's certainly possible that the new RSLinx topics are requesting more data than the DH485 network can handle. The first thing I would do is see if you can use RSLinx/RSWho to read the diagnostic counters on the DH485 port to see if there are physical data link layer errors occurring on the network.

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Just a further thought on this, one of the older engineers has mentioned that it might be because we are running a newer version of RSLinx? Does that sound likely? Legacy system runs 2.6 new system is in the 3s?

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Ok, so I meant 2.52 not 2.6. I have now tried a seperate VM running XP and 2.54 (the oldest version I could get from the download centre.) no difference, the exact same behaviour. This cements the theory that the issue is to do with the 485 network struggling with the new gateway hardware. I had no option but to set up messaging between all these PLCs and the one SLC/500 5/05. This is now my SCADA master for all tags. Not ideal but the only way to do it without rewiring the site network. Not even Rockwell could work it out. Cheers for trying

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