An advanced application of the PCB testability design and rating system

The results of a previous Rome Air Development Center (RADC) Testability effort yielded a printed circuit board (PCB) testability evaluation/rating procedure. This paper presents the results of an effort to expand the methodology derived in the previous study for application to the module, equipment and subsystem level is presented. A discussion of the makeup and composition of the final 'accessibility model' is presented. This model consists of a system of node-valued weighted graphs, (a node being each individual PCB in the system), and an identification for each path from an input to an output in the system. Each path is scored based on the number of nodes in the path and each node's independent and system-dependent testability. The overall system testability is a weighted average of all the path testability scores. The developed model has been computerized and includes the ability to handle feedback loops.