On using twisted-ring counters for testing embedded cores in system-on-a-chip designs

We present novel test set encoding and pattern decompression methods for core-based systems. These are based on the use of twisted-ring counters and offer a number of important advantages-significant test compression (over 10× in many cases), less tester memory and reduced testing time, the ability to use a slow tester without compromising test quality or testing time, and no performance degradation for the core render test. Surprisingly, the encoded test sets obtained from partially-specified test sets (test cubes) are often smaller than the compacted test sets generated by automatic test pattern generation programs. Moreover, a large number of patterns are applied test-per-clock to cores, thereby increasing the likelihood of detecting non-modelled faults. Experimental results for the ISCAS benchmark circuits demonstrate that the proposed test architecture offers an attractive solution to the problem of achieving high test quality and low testing time with relatively slower, less expensive testers