To deterministically detect a Stuck-At-1 (SA1) fault on the single output of a 2-input XOR gate (Inputs A and B), which of the following input test vectors (A, B) must be shifted into the scan chain?
To test for a Stuck-At-1 fault, you must drive the node to its opposite logic state (logic 0) and propagate that result to an observable point. A 2-input XOR gate evaluates to 0 only when both inputs are equal. Therefore, applying either (A=0, B=0) or (A=1, B=1) will nominally drive the output to 0. If the output is physically stuck at 1, the test circuitry will observe a 1 instead of the expected 0, successfully detecting the fault.
