I am starting a new project to upgrade a manufacturing suite that consists of four PLC5/Es. Each major piece of equipment has its own PLC (dryer,mixer, solution kettles). The SCADA is Wonderware InTouch 7.0 on NT. My plan is to upgrade SCADA (probably WW 9.5) and replace the PLCs with one Controllogix using distributed I/O. My question revolves around the I/O racks. Downtime is a very big issue so I thought I would leave the existing 1771 I/O racks and either replace the PLC with a ControlNet adapter or use a Profibus card as a slave in the PLC rack. I would then have to maintain the PLC5s but simplify the program just for block transfers and data concentration. The other advantage would be that I could install the Profibus cards and connect into the Controllogix for testing. If there are issue, I could easily go back to the old state. I have a lot of experience with profibus and feel confident with installing it. Not so with ControlNet. However, it would seem more logical to use the ControlNet setup eliminating the PLCs. Any thoughts? Thanks.