ELECTRICAL-DIAGNOSIS METHOD FOR A DEFECT CELL IN A CHAIN OF CELLS OF A SHIFT REGISTER

摘要

The rank of a defective cell in a level-sensitive scan-design chain within the functional element (13) is found by a static (FLUSH mode) test, applying a square wave from a 20 kHz generator (15). This also triggers a digital storage oscilloscope (11) connected to a computer (12) by a IEEE 488 interface bus. The power supply (14) is connected via a small series resistor (R) with a large shunt capacitor (C) for noise redn. Master flip-flop clock inputs (A,C) are set at 1 and zero respectively, and a slave flip-flop clock input (B) at 1. Current variations are displayed as the input datum is propagated along the chain. In this signature a period of constant current indicates that the last cell to be loaded with the input datum is faulty.