Broadcasting test patterns to multiple circuits

Scan designs can alleviate test difficulties of sequential circuits by replacing the memory elements with scannable registers. However, scan operations usually result in long test application time. Most classical methods to solving this problem either perform test compaction to obtain fewer test vectors or use multiple scan chain design to reduce the scan time. For a large system, test vector compaction is a time-consuming process, while multiple scan chains either require extra pin overhead or need the sharing of normal I/O and scan I/O pins. In this paper, we present a novel test methodology that not only substantially reduces the total test pattern number for multiple circuits but also allows a single input data line to support multiple scan chains. Our main idea is to explore the “sharing” property of test patterns among all circuits under test (CUT´s). By appropriately connecting the inputs of all CUT´s during the automatic test-pattern generation process such that the generated test patterns can be broadcast to all scan chains when the actual testing operation is executed, the above-mentioned problems can be solved effectively. Our method also provides a low-cost and high-performance method to integrate the boundary scan and scan architectures. Experimental results show that 157 test patterns are enough to detect all detectable faults in the ten ISCAS´85 combinational circuits, while 280 are enough for the ten largest ISCAS´89 scan-based sequential circuits