Is the technical staff intimately familiar with the existing logic? If so, it may be easier to maintain translated code than to learn a new program.If the code is no longer needed, delete it. How much of the program is still applicable? There may be equipment included in the program that no longer exists, leaving “dead code” for disconnected inputs and outputs.Is there a document that explains how the program is organized and how it works, maybe in a technical manual from project commissioning?.Is the source well documented with rung comments and meaningful symbol names?.Is the source code available in editable form, i.e., the program and programming software exists electronically?.The usefulness of converting an existing program depends on its condition. It is possible to have custom software written to do the conversion, or just do it manually (which may not be practical for a large program) but these alternatives may add significant cost. If you are switching brands, translation tools may not be available. But is that the correct answer? While it may not take much time to run a translation tool on the old code to create the new, how much extra work is required to get the new program fully operational? Most translation tools will have the disclaimer that they don’t translate 100 percent of the code and have a fairly long list of items that need to be manually handled - and this is if you’re staying with the same manufacturer. Why convert compared with rewriting the software? The quickest answer is cost. What are the pluses and minuses of converting code compared with rewriting it? Why are some systems well suited for this approach and others problematic? This article looks at some of the issues related to converting PLC code and provides some insight into ways to capitalize on this technology without some of the problems that may result. Now to give credit where credit is due, very few people would actually believe a control system upgrade would be this easy. Sounds great, doesn’t it? Buy the new programmable logic controller (PLC) equipment, run the old PLC code through a translator program, and the new system is up and running. Converting Old PLC Code: Benefits and Pitfalls

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