| 摘要 |
PURPOSE:To prevent the change of internal state of an FF although the contents of the FF are read out of a scan-out terminal, by attaining the constitution of a ring-shaped shift register for all FFs within a logical IC. CONSTITUTION:When selection signal terminals 52 and 53 are set at logic 1, selectors 58-60 select the signals given from signal lines 72-74. While a selector 61 selects a signal to be applied to a scan-out terminal 55, i.e., an output signal 77 of an FF62. Therefore FF62-65 are formed in ring-shaped shift registers respectively. When a clock is supplied to a clock input terminal 51 at this time point, the contents of FF62-65 can be read out of the terminal 55. In addition, the contents of FF62-65 are reset to the original states after one rotation when the clock is supplied four times since those FFs are connected in a ring form. |
