The process-oriented programming is a paradigm based on the process concept where each process is a concurrent finite state machine inside. The paradigm is intended for PLC (programmable logic controllers) developers to write Industry 4.0-enabled software. The poST language is a promising process-oriented extension of the IEC 61131-3 Structured Text (ST) language designed to provide a conceptual consistency of the PLC source code with technological description of the process under control. This language combines the advantages of FSM-based programming with the standard syntax of the ST language. We propose transformational semantics of poST providing rules for translation of poST language statements to Promela -- the input language of the SPIN model checker. Following these semantic rules, our Xtext-based translator outputs a Promela model for the poST program. Our contribution is a method for automatic generation of the Promela code from poST control programs. The resulting Promela program is ready to be verified with SPIN model checker against linear temporal logic requirements to the source poST program.