Properties of Memory Faults in Sequential Machines.

摘要

A memory fault is a fault that affects only the next-state function of the machine,and is defined by the fact that the next-state of the faulty machine for some present-state of the good machine for the same present-state and input. Thus memory faults can be defined by an associated mapping F of the state set into itself. A set of necessary conditions for reset equivalence between memory faults is specified,and becomes sufficient upon adding an extra requirement. The most important type of memory fault is the memory-stuck-at (MSA) fault,where one or more lines carrying the state information are stuck at some fixed logical value. By means of a brief analysis of various types of memory elements (flipflops,etc.),it is shown that most stuck-at faults in the memory elements can be modeled as MSA faults,while the few stuck-at faults that are not MSA faults usually cannot be considered as memory faults at all.