| 摘要 |
PURPOSE:To improve the trouble detecting rate of a whole circuit by separating an internal bus output signal and a pseudo-internal bus signal according to a selecting signal. CONSTITUTION:A second selector circuit 11 is provided to select whether the internal bus output signal is set in a scan pass system flip-flop circuit 1, the pseudo-internal bus output signal is held or a scan pass signal by shift operation is set according to a shift operation control signal and the selecting signal. A third selector circuit 31 is provided to select whether the selecting signal is held in a scan pass system flip-flop circuit 3 for test control or the scan pass signal by the shift operation is set according to the shift operation control signal. Then, a first selector circuit 2 separates the internal bus output signal and pseudo-internal bus output signal by the selecting signal. Accordingly, the observation of the internal bus output signal can be easily executed and a limit to be given to bus activation in the circuit can be canceled. Thus, the trouble detecting rate of the whole circuit can be improved. |
