I have implemented a number of conversions and address the task much like a new machine program design. If you have a huge, complicated PLC-5 project, converting to Logix is not a simple conversion. You are sure to run into issues in which the old program was slow enough to execute but the new program will probably have operational gaps where nothing happens because the old code was slow enough. Additionally, the Compact and ControlLogix PLCs execute faster and differently than PLC-5. PLC-5 and SLC-500 and Micrologix1200 are I/O based PLCs, whereas Control and CompactLogix PLCs are tag-based. Keep in mind that PLC-5's are completely different than Logix platforms.
