| 摘要 |
PURPOSE:To diagnose LSIs with high circuit integration in details, by designating a desired tri-state gate and preventing bus fight, through the provision of a control FF and a gate at diagnosis. CONSTITUTION:A logical device is constituted with the 1st group FFs 4-8 being an object of scan-in or scan-out and a plurality of tri-state gate 1-3 controlled with the output of the FFs 5-7 and commonly connected with the output. Further FFs 11 and 12 for control at diagonosis being the objective of scan-in and an nC1 decoder 13 decoding the output of the FFs 11 and 12 are provided. Gates 17-19 are provided at the output side of the decoder 13, the output of the decoder 13 is made all ineffective at the scan operation, and transmitted as it is at diagnosis and the gates 1-3 are made effective in all states not for the case. The output of the decoder 13 designates one of the gates 1-3 and tests the operation of the value of the FFs 5-7. |
