IEC 61131-9 Ed. 1.0 b:2013

IEC 61131-9:2013 specifies a single-drop digital communication interface technology for small sensors and actuators SDCI (commonly known as IO-Link), which extends the traditional digital input and digital output interfaces as defined in IEC 61131-2 towards a point-to-point communication link. This technology enables the transfer of parameters to Devices and the delivery of diagnostic information from the Devices to the automation system.