TESTING OF FAULT-TOLERANT HARDWARE THROUGH PARTIAL CONTROL OF INPUTS

The problem of testing fault-tolerant redundant digital systems is inv estigated. To test redundant systems through normal voter outputs, ind ependent control of the output of each replicated unit is required. In the past it was assumed that independent control of the output of a r eplicated unit requires independent control of all of its inputs. We s how that partial control of inputs is actually required. The critical input set problem, which is the problem of finding a set of inputs tha t need to be independently controlled, is formulated. Solutions are of fered for different testing strategies, including exhaustive testing a nd deterministic testing, and for different levels of circuit descript ion.