An implementation approach of the IEEE 1149.1 for the routing test of a VLSI massively parallel architecture

This paper presents an implementation approach for the test of routers in a fine grain massively parallel architecture. First, an ad hoc test technique which diffuses test messages router by router is analyzed. Even though the technique does not add hardware, it is shown inefficient and not applicable due to practical constraints such as the limited number of pins of the chip implementing the machine. Based on a hierarchical implementation of the IEEE 1149.1 standard, two approaches are proposed and compared in terms of the area overhead, the overall test time and the flexibility in applying tests and diagnosing the routers inside the machine. The basic idea for both approaches is to construct groups of basic cells which are driven by the same test block and compare their test results after the same test vectors are applied at each cell input. The two approaches differ in the granularity of a basic cell. The choice of an implementation approach is not trivial. It is shown that each approach presents better performance than the other, that is, the approach which allows better fault coverage and less test time requires more silicon and less diagnostic possibilities compared to the second approach.