| 摘要 |
PURPOSE:To write and read contents of flip flops other than faulty flip flops by constituting a logic integrated circuit to that all flip flops in this circuit can be shifted in many directions. CONSTITUTION:If one optional flip flop, for example, 21 out of flip flops 20-22 does not function, the first and the second selecting signal terminals 9 and 10 are set to logical '1' and '0' respectively to constitute a scan path, and contents of the flip flop 22 are read out from a scan output terminal 12, and a signal applied to a scan input terminal 8 is written in the flip flop 20 simultaneously. Further, selecting signal terminals 9 and 10 are set to logical '1' together to constitute a scan path, and a shift register in the order opposite to said order is constituted. The signal applied to the scan input terminal 8 is written in the flip flop 22, and contents of the flip flop 20 are read out from the scan output terminal 12 simultaneously.
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