| 摘要 |
PROBLEM TO BE SOLVED: To provide a frequency monitoring apparatus for normally operating even in the case that a testing frequency set value is sequentially switched at a high speed. SOLUTION: In a frequency monitoring circuit of a semiconductor tester comprising a period generator for generating a period signal 16a, and a deciding means for supplying a signal of a frequency of the period signal to a measuring device to compare a waveform from the measuring device with an expected value waveform to decide whether the waveform from the measuring device coincides with the expected value waveform or not, the period generator has a set value memory means 17 for storing a frequency set value, a limited value memory means 17 for storing a frequency limited value, a comparator 18 for comparing the frequency set value with the limited value prior to a semiconductor test to output a detection signal when the set value exceeds the limited value, a detection signal memory means 19 for storing a detection signal prior to the semiconductor test, and a detection signal output means 19 for outputting a stored content of the detection signal memory means synchronously with generation of the period signal when semiconductor is tested.
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