Manuscript received August 30;
1996;
revised January 22;
1996. This work was supported by ARPA under Contract J-FBI-92-194 and the Semiconductor Research Corporation under Contract 95-DJ-703. The authors are with the Center for Integrated Systems;
Stanford University;
Stanford;
CA 94305-4070 USA. Publisher Item Identifier S 0018-9200(97)03836-5;