On Tue, May 14, 2002 at 08:43:44AM -0500, Corey R Clingo wrote: > > > One characteristic of most DCS PLC gateways is that the output values are > silently read back behind the scenes so the operator is able to see exactly > what is in that PLC. This causes confusion sometimes (i.e., when operator > actions have no effect because the PLC logic obliterated their change), but > is a reflection of the real world, and helps in situations like this. I > believe the Integrator 30 at least behaves in this manner. > I think I'm begning to gat a picture of how this should work. However I still have a rather basic question. How can I read a value from the PLC, and increment/decrement this value to write it back? If the AIN in the gateway is in auto, I can't change the value in the DCS, right? If instead, i make a copy, modify it, and write that back to the PLC, which then detects the new data, and sends it back to the AIN, that I am modifying, don't I have a timing race? -- "They that would give up essential liberty for temporary safety deserve neither liberty nor safety." -- Benjamin Franklin _______________________________________________________________________ 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