| 摘要 |
PURPOSE:To facilitate the easy diagnosis regardless of the scale of the logical circuit group by comparing the state data fed from a register with the normal state data of the logical circuit group, and diagnosing the normal operation of the logical circuit group with the coincidence signal outputted when the compared result of both data is coincident. CONSTITUTION:A shift register 1 is connected to a combined circuit having a prescribed function and a logical circuit group 2 containing sequence circuits. This register 1 is used as set the test data to be applied to the group 2 and the state data of the group 2 and driven by a scan clock 5 and a system clock 6. In addition, the register 1 contains a terminal for input of test data and a terminal for output of state data. An exclusive OR circuit 3 uses the scan input and output signals as the input and a signal ''1'' as a comparison output 8 only when no coincidence is obtained between both scan input and output signals. Thus the diagnosis is possible with no increment of the load to a diagnosing device depite of an increment of scale of a logical circuit. |
