semiconductor device testers are provided which measure skew between two or more output pins of a semiconductor device independent of a strobe timing input . more particularly , a skew signal is generated by a comparator circuit that changes state when the respective outputs transition state , for example , from matching to differing states . in a two output pin embodiment , for instance , when one of the output pin changes state before the other and both initially are in the same state , a flip flop is set at the time when the data on the output pins first differs , i . e . when the first output pin transitions to a new state . the flip flop is then reset when the second output pin subsequently transitions to the new state and again matches the first output pin . the resulting duration of the output of the flip flop thereby corresponds to the time of skew of the output pins regardless of the initial state of the pins .