A self-synchronising data bus analyser comprising a generator LFSR, a receiver LFSR and a comparator wherein the generator LFSR generates a first data set which is transmitted through a data bus to the comparator; and wherein the comparator compares the first data set with a second data set generated by the receiver LFSR and adjusts the receiver LFSR until the second data set is substantially the same as the first data set.