We have quite a few multidrop setups going to Integrator 30's. I have used the Black Box ME837A, RS-232/RS-485 copper line drivers with good success. They are also optically isolated to help eliminate grounding problems. http://www.blackbox.com/Catalog/Detail.aspx?cid=3D381,1452,1465&mid=3D111= 9 =20 On a recent project I switched to ME540A fiber line drivers. These devices will connect to a copper RS-232 or RS-485 devices and then do the multidrop on the fiber side. Because the multidrop is done between the modems it is a lot easier to deal with devices that don't handshake well. They are a little more expensive but worked so well that I am planning to stick with this setup in the future.=20 http://www.blackbox.com/Catalog/Detail.aspx?cid=3D381,1452,1470&mid=3D118= 6=20 Regards, Terry Terry J. Deo Infineum USA, L.P. Bayway Chemical Plant Linden, New Jersey 07036 Ph: 908-474-6179 Email to: terry.deo@xxxxxxxxxxxx -----Original Message----- From: foxboro-bounce@xxxxxxxxxxxxx [mailto:foxboro-bounce@xxxxxxxxxxxxx] On Behalf Of Johnson, Alex P (IPS) Sent: Wednesday, September 05, 2007 8:51 PM To: foxboro@xxxxxxxxxxxxx Subject: Re: [foxboro] Modbus Multidrop I've normally used Black Box. Their free technical support is awesome. Just call them and they will tell you what you need. www.blackbox.com From their website: http://www.blackbox.com/Tech_Support/Index.aspx Telephone: 724-746-5500 Answered in 20 seconds or less! Fax: 800-321-0746 Answered in 15 minutes or less! e-mail: Send an e-mail. Answered in 15 minutes or less! Online: Talk to Tech Answered in 20 seconds or less! Who says there is no money in hardware? :) Regards, Alex Johnson Invensys Systems, Inc. 10900 Equity Drive Houston, TX 77041 713.329.8472 (voice) 713.329.1700 (fax) 713.329.1600 (switchboard) alex.johnson@xxxxxxxxxxxxxxxx -----Original Message----- From: foxboro-bounce@xxxxxxxxxxxxx [mailto:foxboro-bounce@xxxxxxxxxxxxx] On Behalf Of Airhart, Chad M. Sent: Wednesday, September 05, 2007 2:36 PM To: foxboro@xxxxxxxxxxxxx Subject: [foxboro] Modbus Multidrop We have two Foxboro Integrator 30's for connection to devices with Modbus. I now have to connect multiple devices to each Modbus integrator so I want to do a multidrop for each. Each integrator connects to a P0970VB configuration selector. The manual shows that card going to a J478 or J878 modem then modbus bus connected to a J478 or J878 modem at each device. The only J478 or J878 modems I found on the internet look like 1970's vintage boxes. How are you guys doing multidrop (where each connected device is via RS-232) and with which equipment (vendor/model numbers)? Looking for standard off the shelf equipment if possible. Any help would be appreciated. Chad M. Airhart Principal Engineer - Lyondell Chemical Co. Instrument, Electrical and Control Systems Engineering Victoria Plant Ph. (361)572-2568 Fx. (361)572-2541 Cell. (361)935-3230 _______________________________________________________________________ This mailing list is neither sponsored nor endorsed by Invensys Process Systems (formerly The Foxboro Company). Use the info you obtain here at your own risks. 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