1 Basic Principles of PLC Ladder Diagram MPP is recognized as “└”. Using the method given above for the analysis cannot be wrong. However, MPS sometimes the compiling program will ignore the same output status, as shown in the figure. MPS MRD MPP MPP 7. STL instruction: Used for designing the syntax of the sequential function chart (SFC). STL instruction allows the program designer a clearer and readable picture of the sequence of the program as when they draw a sequence chart. From the figure below, we can see clearly the sequence to be planned. When the step S moves to the next step, the original S will be “Off".
Such a sequence can then be converted into a PLC ladder diagram and called “step ladder diagram”. M1002 8. RET instruction: Placed after the completed step ladder diagram. RET also has be placed after STL instruction. See the example below. S20 S X1 S20 X1 RET S RET See step ladder instructions [STL], [RET] in Ch. 4 for the structure of the ladder diagram. DVP-PLC Application Manual 1-11 M1002 SET S0 S0 S SET S21 S21 S SET S22 S22 S S0 RET SET S0 SET S21 SET S22