Recently the desire for safety networks has been increasing in order to reduce the amount of wiring in safety systems. The compatibility of safety devices such as light curtains and safety switches having safety networking ability reduces the amount of wiring, cost and installation labor.
IEC61508 SIL3 requires less than 10-7 of undetected communication failure rate. CC-Link Safety meets that requirement and will detect communication failures that may cause malfunction of the emergency stop operation. This fail-safe function will bring machinery into a safe condition quickly if a communication failure is detected. This is accomplished by adding a safety function layer on the upper level layer of the CC-Link protocol that detects each transmission error. Information for the safety function layer includes a “running number” to specify message order and CRC32 to detect an unreadable message bit.