Modern integration separates PLC-specific connectivity from MES logic so the systems can evolve independently.
PLC → OPC UA / adapter → edge gateway or integration layer → normalized equipment model → MES.
Machine, line, unit and source tag.
Data type, scaling, units and precision.
Order, batch, material, state and operation.
Timestamp, communication status and data quality.
Compare MES values with the source, test communication loss, verify timestamps and units, and keep command paths separate from monitoring paths.