| 摘要 |
PURPOSE:To attain the same scan-in/out control operation with simple constitution even if number of FFs constituting scan chain is changed by connecting a shift register comprising prescribed FFs to constitute a scan loop. CONSTITUTION:A shift clock counter circuit 13 is cleared before the start of the scan-in/out control operation. The content of the FF of scan chain is shifted the same as a conventional method until n2-set of shift clocks is applied in this state. A signal A from the counter circuit 13 is set at the n2-th time. Then the signal A is being set until mXk-set of shift clocks is applied and the state of n1, n2-set FFs is unchanged because the shift clock is suppressed in the scan chain. On the other hand, m-set of FFs become the scan chain closed by m-set and after mXk-sets of shift clocks are applied and then the state becomes the original state. |
