The signal state that a signal of interest within a system under test has during each of a plurality of cycles of operation of the system under test is stored in a trace file. In association with the signal state, information regarding a requested access to the signal state by a control program during a particular cycle among the plurality of cycles is also stored. From the trace files a presentation is generated that presents, for at least a signal of interest within the system under test, a plurality of signal state indications, each indicating a respective state that the signal had during a one of a plurality of cycles of operation of the system under test. The presentation also indicates, in a graphically distinctive manner, at least one cycle of operation during which a control program requested access to a state of the signal, so that the influence of the control program on the state of the system under test is visually apparent.