The way of ladder diagram analysis for small compact programmable controller

The paper presents the considerations relating to the methods of analysis of a ladder diagram created for a small programmable controller (PLC) of compact type which is equipped with a simple keyboard for entry of such a diagram. Because of the fact that the compact PLC was built using a standard microcontroller with small calculation power the authors met difficulties with the translation of the control program to the binary code. It was necessary to make a decision that a ladder diagram would be not compiled but interpreted during program execution. The method of column by column analysis of the ladder diagram was chosen as the most effective. The particular application of this method for a small compact PLC is presented in detail in the paper.