A XOR-tree based technique for constant testability of configurable FPGAs

This paper presents a novel approach for testing and diagnosing configurable field programmable gate arrays (FPGAs). The proposed approach is row-based and uses a two-session procedure. The approach arranges some logic blocks to be programmed as XOR-tree (or chain, or cascade) in the first session. The XOR-tree is effectively used as test vehicle for observability. The roles of the CLBs are inverted in the second session. It is shown that the proposed testing arrangement requires a number of tests independent of the number of CLBs in the FPGA (i.e. C-testability is accomplished). Routing is kept local, and compatibility for a CAD implementation is also accomplished.