I used a LIFO on a vessel that was filled + extracted from the bottom. The control system had to monitor each tanker that was offloaded into the storage vessel (which had the capacity to store about 5 tankers worth). Each offload had to register an entry into the LIFO with the current level of the tank and the eventual end level once the offload had finished. I then used this information to remove the entry from the LIFO, once the tank level had fallen to the value contained within each LIFO entry. I also had to store a lot number for product traceability purposes, which forced me to build my own block attaching x number of datawords to each LIFO entry.
FIFO Demonstration for RSLogix500 (using LogixPro)
Stu, Here is a short RSLogix500 FIFO Load and Unload demonstration (written in LogixPro simulator). You will see that it unloads to Output O:2 in the same order as it loaded (Binary 0 to 100). As the FFU Position indicator (R6:2) counts down from 100 to 0, the Output goes from 0 to 100.