Shift Register Instructions. FFL FIFO Load FFU FIFO Unload LFL LIFO Load LFU LIFO Unload The FIFO is a First In First Out Register used to buffer data. The LIFO is a Last In First Out Register used as a stack. FIFO Load (FFL).
used as a stack
For asynchronous type lines, such as pallet (assembly) lines in which individual pallet are stopped and released in zones, the FIFO instructions are a better choice for a data tracking system than the LIFO instructions. The designers must be careful to never let the FIFO get out of sync because it’s not self-clearing and will cause data to be skewed forever until the FIFO is clear
One of the main uses of LIFO instruction is for the temporary storage of data words between functions or process when tracking item on a stack. One program can save a block of data in an array and then allow a second program or process to retrieve the data when control is passed to the other program