| 摘要 |
PURPOSE:To accurately measure a noise margin by dividing one pattern among the input patterns of a semiconductor device and applying different voltage values to divided segments. CONSTITUTION:A modified pattern B is generated such that one pattern of an original patterns A is divided into two and input voltages VIH' or VIL' and VIH or VIL are applied to the first and second halves of the divided original patterns, respectively. Input patterns are changed over at timings (a), (b), (d), (f), (i), and (j). A large current flows in a semiconductor device with relation to the timings, resulting in a voltage drop and the like, and a malfunction is apt to be caused in the semiconductor device. By setting the H level of the timings (a), (d) and (i) to VIH, higher than the voltage VIH of the pattern A and setting the L level of the timings (b), (f) and (j) to VIL' lower than the voltage VIL of the pattern A, the operation of the semiconductor device is stabilized because the H and L levels are not operational critical values. At the timing whereat the operational critical value is applied, the input pattern is not changed over from H to L or from L to H. Therefore, there arises no power supply voltage drop and the like and the operational critical values VIH and VIL representing noise margin can be measured.
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