If you are using a gateway for communication between I/A & PLC5, use two files in the PLC for data transfers. The first for DCS read values (PLC write) and the second for DCS write values (PLC read). This will save you the effort of masking bits/registers to and from the PLC. If you believe that timing issues remaing, at least you have eliminated one possible culprit - systems overwriting one another. Stephen T. Woodworth, P.E. FeedForward, Inc. 1341 Canton Road, Suite H1 Marietta, GA 30066 770.426.4422 mailto:swoodworth@xxxxxxxxxxxxxxx _______________________________________________________________________ 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