What special considerations apply to safety PLC programming?

Safety PLC programming considerations: use certified safety platforms (IEC 61508, IEC 62443), implement single-fault tolerance, avoid conditional logic that could bypass safety, use dedicated safety I/O modules, maintain separation from standard control. Programming practices: avoid complex logic (simple = verifiable), no online editing during operation, formal testing and validation, documented proof test procedures. Include diagnostics, watchdog monitoring, and safe state definition. Program changes require MOC process and SIL verification. Regular proof testing per SIL requirements. Safety and standard programs must be independent to maintain SIL integrity.