Joe, We have exactly what you are looking for. We are using a DI30B (Device Integrator 30-B), with a Modbus ASCII/RTU Slave software license. The license supports a limited number of AI, AO, DI & DO (in our case 50 AI, 50 AO, 50 DI, 50 DO). Our system is I/A NT 6.5.1. You will need 2 disks for configuration, for 6.5.1 and DI30B the numbers are #72901 and #72902. You will also need a manual called "Protocol Reference Guide -Modbus Slave Protocol Device Integrator", which I beleive is only available in print (I couldn't find it in the electronic documentation CD, it doesn´t even have a doc. number). You should also be careful not to use the B0193MS (Device Integrator 30) manual, it is very confusing and not Modbus-specific. Once your module is installed and running, the programming is quite difficult. If you choose to use this solution, I can send you more information on how to program the DI30B (you could also use a DI15 or a DI30). I've been reading the other replies, some of them suggest the OMNII-COMM (Miille Applied Research) or the MCM PROSOFT (Prosoft-technology) protocol modules. These modules work with the Allen Bradley PLC, and in both cases you would need an AB chassis, power supply and CPU. I think the DI30 is a simpler solution. I hope this information is useful for you Regards, Pablo Lioi Systems Engineer TOTAL AUSTRAL CAÑADON ALFA-RIO CULLEN Tierra del Fuego - Argentina. _______________________________________________________________________ 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. Read http://www.thecassandraproject.org/disclaimer.html foxboro mailing list: http://www.freelists.org/list/foxboro to subscribe: mailto:foxboro-request@xxxxxxxxxxxxx?subject=join to unsubscribe: mailto:foxboro-request@xxxxxxxxxxxxx?subject=leave