Fault effects in asynchronous sequential logic circuits
Ming‐Der Shieh, C.-L. Wey, P.D. Fisher · IEE Proceedings E Computers and Digital Techniques · 1993
The paper demonstrates the effects of single stuck-at faults in Huffman-model asynchronous sequential logic circuits (ASLCs). The fault effects include equivalent-state redundant faults, invalid-state redundant faults and state oscillations. Equivalent-state redundant faults in ASLCs may be generated by violation of the fundamental mode constraint noncritical races or delays. On the other hand, invalid-state redundant faults are caused either by the existence of invalid states, or by improperly assigning the ‘don't-care’ terms. State oscillations are generally caused by the presence of critical races. Based on the fault effects, this paper presents a set of rules for synthe-sising oscillation-free ASLCs in the presence of faults. As far as synthesising testable ASLCs is concerned, the race-free UDC state assignment is much better than STT state assignment.