Testing the configurable interconnect/logic interface of SRAM-based FPGA's

Abstract

The objective of this paper is to define a minimum number of configurations for testing the configurable modules that interface the global interconnect and the logic cells of SRAM-based FPGAs. In usual SRAM-based FPGAs, Configurable Interface Modules (CIMs) can be found between the global interconnect and inputs of the logic cells (input CIMs) or between output of the logic cells and the global interconnect (output CIMs). It is demonstrated that an input CIM that connects N/sup in/ segments to a logic cell input requires N/sup in/ test configurations and that an output CIM that connects a logic cell output to N/sup out/ segments requires 2 test configurations. Then, it is proven that a set of K/sup in/ input CIMs can be tested in parallel making the number of required test configurations equal to N/sup in/. In the same way, a set of K/sup out/ output CIMs is shown to require only 2 test configurations if N/sup out/>K/sup out/. Finally, it is shown that the complete mXm array of logic cells with K/sup in/ input CIMs and K/sup out/ output CIMs can be tested with only N/sup in/ test configurations using the XOR tree and shift register structures.