A communication unit (S1, S2) for industrial automation for use in a communication system (10) of series-connected communication units (M, S1, S2). The communication unit includes a first input (E1), a first output (A1), and an internal clock generator (TG) which is adapted to provide an internal clock signal as system clock for clocking the communication unit (S1, S2), and wherein the communication unit (S1, S2) is configured to receive, via the input (E1), a serial input data stream with payload data. The communication unit (S1, S2) has a timer (ZG) for providing a time value, the timer (ZG) being adapted to provide the time value based on an input symbol clock included in the input data stream.