Method, computer program and apparatus for analysing a programmable logic controller program

A Programmable Logic Controller Program analysis method comprising:

• translating (TRANS) an original program (PROG) of the type of a Programmable Logic Controller (PLC) Program which is a Ladder program, into a model (MOD) in a logical framework by using predefined modelizations of Ladder primitives;
• determining, from at least said model (MOD) and predefined language formalization, a set of properties (Prop) on internal variables of said original program;
• verifying, by an automated solver (SMT), satisfiability of said set of properties (Prop) coupled with user specifications (IntProp) and providing, if contraposition of a property (Prop) from said set of properties (Prop) is satisfiable, a set of counter-examples (PROOF NOK) representative of model inputs and internal memory values for which said property (Prop) contraposition is satisfiable, or providing, if said set of properties (Prop) is always satisfied, confirmation (PROOF OK) thereof;
• translating counter-examples (PROOF NOK), into error initial configurations (IniConf) of said model, said error initial configurations (IniConf) comprising initial values of inputs and initial values of internal memory;
• simulating an execution (EXE) of the model with error initial configurations (IniConf) of said model, and recording error intermediary configurations (AST-IntConf) of said model simulation, from the beginning of execution up to said property violation, said intermediary configurations comprising intermediary values of internal memory;
• translating said error initial configurations (IniConf) of said model and said error intermediary configurations (AST-IntConf) of said model simulation, into error initial and intermediary configurations (Lad-IniConf, Lad-IntConf) of said original program (PROG);
• and displaying said error initial and intermediary configurations (Lad-IniConf, Lad-IntConf) with an indication of a location of an error in said original program (PROG).