An input/output (I/O) block for a semiconductor integrated circuit (IC), which includes: at least one I/O buffer, configured to define at least one signal path in respect of a connection to a remote I/O block via a communication channel, each signal path causing a respective signal edge slope; and an I/O sensor, coupled to the at least one signal path and configured to generate an output signal indicative of one or both of: (a) a timing difference between the signal edge for a first signal path and the signal edge for a second signal path, and (b) an eye pattern parameter for one or more of the at least one signal path.