BIST TPG for combinational cluster interconnect testing at board level

A novel built-in self-test (BIST) architecture and a test pattern generator (TPG) design methodology to program this architecture are presented for inter-IC interconnects among combinational non-boundary scan ICs (often called cluster-ICs) via IEEE 1149.1 boundary scan architecture (BSA). Due to the expense and complexity of BSA circuitry, cluster-ICs are still widely used in modern circuit boards. Since combinational logic and 3-state cluster nets exist within cluster interconnect, in order to test all detectable faults in inter-IC nets that include cluster-ICs, newly identified TPG requirements are used to guarantee fault coverage during the design of proposed BIST architecture. This architecture contains a two-level C-TPG that generates constrained pseudo-random patterns for boundary scan cells (BSCs) of cluster control cones, a D-TPG that generates patterns for BSCs of cluster data cones, and a look-up table which is programmed to select, for each BSC, a specific C-TPG or D-TPG stage whose content is shifted into that BSC. This test architecture provides a true BIST solution for cluster testing. The proposed methodology generates TPGs that (i) guarantee the avoidance of multi-driver conflicts when testing via BSA, (ii) guarantee the detection of all testable interconnect faults, (iii) have low area overheads, and (iv) have short test lengths.