NoC-Compatible Wrapper Design and Optimization under Channel-Bandwidth and Test-Time Constraints

Abstract

The IEEE 1500 standard wrapper requires that its inputs and outputs be interfaced directly to the chip's primary inputs and outputs for controllability and observability. This is typically achieved by providing a dedicated Test Access Mechanism (TAM) between the wrapper and the primary inputs and outputs. However, when reusing the embedded Network-on-Chip (NoC) interconnect instead of the dedicated TAM, the standard wrapper cannot be used as is because of the packet-based transfer mechanism and other functional requirements by the NoC. In this paper, we describe two NoC-compatible wrappers, which overcome these limitations of the 1500 wrapper. The wrappers (Type 1 and Type 2) complement each other to optimize NoC bandwidth utilization while minimizing the area overhead. The Type 2 wrapper uses larger area overhead to increase bandwidth efficiency, while Type 1 takes advantage of some special configurations which may not require a complex and high-cost wrapper. Two wrapper optimization algorithms are applied to both wrapper designs under channel-bandwidth and test-time constraints, resulting in very little or no increase in the test application time compared to conventional dedicated TAM approaches.