The paper presents application of the Grafpol method for synthesis of sequential algorithms of pneumatic drive control. The Grafpol method permits determining an analytic equation to describe the sequential control algorithm. The synthesis procedure consists of a few stages that include determination of the process algorithm, control algorithm, memory and schematic equation. The memory can be determined by analysis of the relationships ... and Y1 related to the memory realisation rules. The methodology of graphic presentation of the ... functions is also described. In consequence, analysis of these relationships makes the ground for determining the functions of all the output variables and elementary memory cells. With these functions it is possible to formulate a schematic equation being the base for the PLC processing program.