JPS6473266A - Logic tester - Google Patents

Abstract

PURPOSE:To enable the picking up of abnormality in the switching of a signal, by providing a hysteresis holding circuit to hold a hysteresis of an output signal waveform of a logic circuit to be tested and a hysteresis deciding circuit to judge the data thereof. CONSTITUTION:An input pattern 31 or the like is inputted into a logic circuit 40 to be tested through a drive circuit 20 from a tester controlling circuit 30. An output 42 from the logic circuit 40 being tested gives the results 33 of decision to the tester controlling circuit 30 as input through a checking circuit 10, which is made up of a threshold generation circuit 13, a comparator circuit 11, a decision circuit 12, an extraction circuit 14, a hysteresis holding circuit 15 and a hysteresis judging circuit 16. Then, the hysteresis judging circuit 16 checks a hysteresis pattern depending on an output of the hysteresis holding circuit 15 using a counter which counts the frequency at which the output signal 42 passes a threshold value and the output of a counter 17 which holds a hysteresis of an expected value pattern 34.