Does anyone know where I could find the description of these function blocks? I can see them under the loadables in the 984PLC configuration, and they are used in the old program, but there's no help file that would define them.
Custom loadables could come from different vendors - at one time there were a lot of vendors creating their own custom loadables. If there is any way you can determine what company created the PLC program or did the integration I would start there.
One of the loadables is named DCSS - does this system work with a DCS? If so then the loadable may have been provided by the DCS manufacturer.