Space Compression Methods With Output Data Modification

The main advantages of space compression are the reduction in the number of pins monitored by the tester and the minimization of the memory space required for reference signatures. Compression, however, may reduce fault coverage. We investigate output data modification with the objective to improve the efficiency of syndrome testing and to reduce by a significant amount the error probability. It was found that this approach to output modification depends strongly upon the functions tested and may result in a complicated testing circuit, in some cases. A design algorithm is proposed which combines space compression and output modification. This algorithm will often minimize the disadvantages of both approaches while maintaining error coverage information.