poST: A Process-Oriented Extension of the IEC 61131-3 Structured Text Language

This paper presents the core concepts for poST language – a process-oriented extension of IEC 61131-3 Structured Text (ST) which intends to provide conceptual consistency PLC source code with technological description plant operating procedure. The can be seamlessly used as textual programming complex software in context ( $3^{rd}$ Edition). combines advantages FSM-based conventional syntax ST would facilitate its adoption. assumes that poST-program is set weakly connected concurrent processes, structurally and functionally corresponding plant. Each process specified by sequential states. states are constructs, extended TIMEOUT operation, SET STATE START / STOP check state operations communicate other processes. describes basic language, demonstrates usage developing control an elevator, compares development pure Text.