Static component interconnect test technology (SCITT) a new technology for assembly testing

Abstract

Modern packaging technology combined with densely populated assemblies requires efficient design for test features. In particular, modern memories with complex interfaces need to be addressed. This paper presents the details of a test technology that makes assembly test more efficient.The method is based on the implementation of XOR and XNOR gates to bypass a functional circuit. It is compatible yet complimentary to Boundary-Scan. Mathematical proof and simulation results show the effectiveness of this method for detection and diagnosis of assembly faults. Known alternatives are compared for test coverage.

IEEE Std 1581 — A standardized test access methodology for memory devices

“…IEEE P1581 was first based on a test logic design known as SCITT[5], originally proposed by Philips and Fujitsu. In IEEE Std 1581 this test logic design is referred to as XOR test logic, which is comprised of XOR or XNOR gates, connecting all test inputs and test outputs, where:…”

Static component interconnection test technology in practice

“…The Verilog file This is an early implementation with two-input XNORs. Although 100% coverage is achieved, which is responsible for detection, it may show slightly less diagnostic capabilities than a realisation with three-input XNORs [2]. Detailed calculation shows a slight increase of the access time by only 0.05 nsec.…”

“…The capability to check the correct functioning of the total I/O buffer after assembly is lost with this method. To maximise diagnostics, each XNOR function must have an odd number of inputs greater than one and each output must have a unique combination of inputs connected [2]. In test mode, SCITT changes the 'complex' memory function into a simple logic cluster containing XNOR functions.…”

“…Finally some remarks on Design for Test (DfT) with respect to SCITT are given in section 13, followed by the concluding remarks. The internal details on the XNOR circuits can be found in an accompanying paper [2].…”