We originally built our system ( one of the earliest IA ) using ladder logic ... I found it easy to use and it kept all the interlock processing at the FBM level. Unfortunately, being able to work with ladder logic seems to be a dying art, and we're switching to non-ladder FBMs and GDEVs and moving interlock processing to IND seq blocks in the CP. I don't like loading up the CPs that way, but it was the only way I could get others to understand what the interlocks were doing. Of course, we're all pre-200 series FBMs, so each card is limited to only 4 pumps and the IFLs wouldn't be a problem with that. Brad Wilson ExxonMobil Chemical Co Edison Synthetics Plant 732-321-6115 732-321-6177 fax Brad.S.Wilson@xxxxxxxxxxxxxx _______________________________________________________________________ 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: //www.freelists.org/list/foxboro to subscribe: mailto:foxboro-request@xxxxxxxxxxxxx?subject=join to unsubscribe: mailto:foxboro-request@xxxxxxxxxxxxx?subject=leave