An Efficient On-Chip Test Generation Scheme Based on Programmable and Multiple Twisted-Ring Counters

Twisted-ring-counters (TRCs) have been used as built-in test pattern generators for high-performance circuits due to their small area overhead, low performance impact and simple control circuitry. However, previous work based on a single, fixed-order TRC often requires long test time to achieve high fault coverage and large storage space to store required control data and TRC seeds. In this paper, a novel programmable multiple-TRC-based on-chip test generation scheme is proposed to minimize both the required test time and test data volume. The scan path of a circuit under test is divided into multiple equal-length scan segments, each converted to a small-size TRC controlled by a programmable control logic unit. An efficient algorithm to determine the required seeds and the control vectors is developed. Experimental results on ISCAS´89, ITC´99 and IWLS´05 benchmark circuits show that, on average, the proposed scheme using only a single programmable TRC design can achieve 35.58%-98.73% reductions on the number of test application cycles with smaller storage data volume compared with previous work. When using more programmable TRC designs, 83.60%-99.59% reductions can be achieved with only slight increase on test data volume.