An Algorithm about Transforming PLC Ladder Diagram to Instruction List Based on Series-Parallel Merging Method

Usually there are 3 steps in transforming PLC ladder diagram to instruction list: including mapping ladder diagram to AOV digraph, transforming AOV digraph to binary trees and transforming binary trees into instruction list. The second step is the most critical and complicated. This paper proposes a method that can transform the AOV digraph to binary trees by using Series-parallel Merging thought, which is visual and easy to realize. An example of transformation is given, which introduced the algorithm and transforming steps.