I am trying to build an inventory management system that receives part numbers(Format, 123-45:67) from a bar code scanner and uses Allen Bradley 1100 PLC to keep a track of parts in stock . I require some help/hints on programming steps, to detect when there is a new bar code scan; write the value (part number) in Channel 0 into a string and clear buffer for next bar-code scan. I do understand that key is to use ARL instruction but I am not able to figure out how to trigger a false to true transition for the same, as there is no traditional input in this case.