Fault detection in CVS parity trees with application to strongly self-checking parity and two-rail checkers

摘要

The problem of single stuck-at, stuck-open, and stuck-on fault detection in cascode voltage switch (CVS) parity trees is considered. The results are also applied to parity and two-rail checkers. It is shown that, if the parity tree consists of only differential cascode voltage switch (DCVS) EX-OR gates, then the test set consists of at most five vectors (in some cases only four vectors are required) for detecting all detectable single stuck-at, stuck-open, and stuck-on faults, independent of the number of primary inputs and the number of inputs to any EX-OR gate in the tree. If, however, only a single-ended output is desired from the tree, then the final gate will be a single-ended cascode voltage switch (SCVS) EX-OR gate, for which the test set has only eight vectors. For a strongly self-checking (SSC) CVS parity checker, the size of a test set consisting of only codewords is nine, whereas for an SSC CVS two-rail checker the size of a test set consisting of only codewords is at most five.