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Technical Report

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Technical Report Number



Exhaustive built-in self testing is given much attention as a viable technique in the context of VLSI technology. In this paper, we present heuristic in order to make exhaustive testing of combinational circuits practical. The goal is to place a small number of register cells on the nets of the input circuit so that the input dependency of combinational elements in the circuit is less than a small given integer k. Our heuristic guarantees that each output can be individually tested with 2k test patterns and can be used as a subroutine to generat efficient test patterns to test all the outputs of the circuit simultaneously. For example, we can connect the register cells in a Linear Feedback Shift Register(LFSR).

Minimizing the number of the inserted register cells reduces the hardware overhead as well as the upper bound on the number of test patterns generated. A heuristic approach has been proposed only for the case when an element in the circuit schematic denotes a boolean gate. An element may, however, also be used to represent a combinatorial circuit model. Our heuristic applies to this case as well. Extensive experimentation indicates that the proposed technique is very efficient.