Use when the user reports a PLC error code, fault, alarm, or diagnostic problem — hex codes like 0x7500, IEC codes like 16#8011, CMMT/CMMT-ST drive faults, CODESYS compile or runtime errors, EtherCAT AL status codes, SDO abort codes, CiA 402 fault state, or "axis won't move / drive shows error".
Use when writing, editing, or refactoring IEC 61131-3 Structured Text — any .st file, Function Block (FB), PROGRAM (PRG), FUNCTION, GVL, ENUM or STRUCT (DUT) for CODESYS, Festo CPX-E, or any PLC task. Also use when the user says "create an FB", "PLC code", "ladder to ST", or asks for machine/automation logic.