A signal capture system and method is used to capture a data signal using a data strobe signal having a preamble of strobe signal transitions. The system includes a data latch circuit receiving the data signal. The data latch circuit is clocked by transitions of the data strobe signal to capture respective bits of data corresponding to the data signal. A decoder receives a memory command signal and generates a data start signal after a delay period from receiving the memory command signal if the command signal corresponds to a read or a write command. The receipt of read or write command signals is used by a control circuit to identify the start of valid read or write data signals. The control circuit then outputs the captured data signals responsive to the data start signal, thereby ignoring the transitions in the preamble of the data strobe signal.