| 摘要 |
PURPOSE:To suppress increase in number of terminal to the minimum so that only necessary circuits can be tested, by performing scan-in and scan-out to an optional state storing circuit group. CONSTITUTION:In order to operate the scanning circuit shown in the figure as an ordinary scanning circuit, an enable signal T, scan-in signal line 2 which is set to an independent mode at '0', and scan-out signal line 7 are turned off by respective transfer gates 4 and 9. Simultaneously, the inverted signal T of the enable signal becomes '1' and the scan-pass 1 from the previous step or scan-pass 8 to the next step is turned on, and then, a state storing circuit group 6, in which several state storing circuits 5 are aggregated, operates as a part of an ordinary scanning circuit. When the circuit is operated as an independent scanning circuit, the enable signal T is set at '1' and the signal lines 2 and 7 are turned on by means of the gates 4 and 9. |
