| 摘要 |
PURPOSE:To make it possible to observe the irregularity of circuit delay time in a chip as well as between chips, by providing a plurality of ring oscillators distributed in a chip and a selecting means which selects one of output signals of the ring oscillators in accordance with an external signal. CONSTITUTION:The following are provided; a plurality of ring oscillator circuits 1-4 distributed in a chip 7 to observe the difference of circuit delay time in a large scale integrated circuit, and a selecting means 6 which selects one of output signals of the ring oscillator circuits 1-4 in accordance with an external signal. For example, when an oscillation indication signal 101 is set as '1', the ring oscillator circuits 1-4 start to oscillate at a time. When ring oscillator circuit selection signals 110 and 111 are input to a decoder circuit 5, the decoder circuit 5 decodes ring oscillator circuit selection signals 110 and 111, and turns one of output signals 112-115 into an active state. The selection circuit 6 outputs one of output signals 102-105 of the ring oscillator circuits 1-4 as an observation signal 120.
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