It is very common for us (Invensys-Arg) to use RS-232 to RS-485 converters = , for Modbus connection from Tricon/Trident to I/A Integrators. Both for mu= ltidrop and also to have longer distances. May be there is a better one in the market, but we always use the ADAM with= perfect results up to now. Saludos, Jos=E9 Acu=F1a -----Original Message----- From: foxboro-bounce@xxxxxxxxxxxxx [mailto:foxboro-bounce@xxxxxxxxxxxxx] On= Behalf Of Jack.Easley@xxxxxxxxxxxx Sent: Lunes, 10 de Septiembre de 2007 01:25 p.m. To: foxboro@xxxxxxxxxxxxx Subject: Re: [foxboro] FW: Modbus Multidrop Our only multi-drop Modbus implementation with an Integrator 30 uses an RS-232 to RS-485 converter, not a modem. Jack Easley -----Original Message----- From: foxboro-bounce@xxxxxxxxxxxxx [mailto:foxboro-bounce@xxxxxxxxxxxxx] On Behalf Of C. M. Airhart Sent: Wednesday, September 05, 2007 9:21 PM To: foxboro@xxxxxxxxxxxxx Subject: [foxboro] FW: Modbus Multidrop FW: Modbus Multidrop I sent this earlier but wasn't sure it made it out. The IT Nazi's have a pretty good grip on our email and internet access. Any help with the Modbus would be appreciated. ______________________________________________ From: Airhart, Chad M. Sent: Wednesday, September 05, 2007 2:36 PM To: foxboro@xxxxxxxxxxxxx Subject: 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)? Does everyone put in 232-485 converters on the devices and I-30? Our P0970VB configuration selector has a 25 pin connector connected to a cable connected to a pigtail to 9 pin 232 connected to our current device. Has anyone used a 25 pin 232 to 485 converter directly off the P0970VB configuration selector? 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 =3D20 =3D20 _______________________________________________________________________ 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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