4.33 When silicon chips are fabricated, defects in materials (e.g., silicon) and manufacturing errors can result in defective circuits. A very common defect is for one wire to affect the signal in another. This is called a “cross-talk fault”. A special class of cross-talk faults is when a signal is connected to a wire that has a constant logical value (e.g., a power supply wire). These faults, where the affected signal always has a logical value of either 0 or 1 are called “stuck-at-0” or “stuckat-1” faults. The following problems refer to bit 0 of the Write Register input on the register file in Figure 4.23.
4.33.1 [10] Let us assume that processor testing is done by (1) filling the PC, registers, and data and instruction memories with some values (you can choose which values), (2) letting a single instruction execute, then (3) reading the PC, memories, and registers. These values are then examined to determine if a particular fault is present. Can you design a test (values for PC, memories, and registers) that would determine if there is a stuck-at-0 fault on this signal