On-chip test generation for combinational circuits by LFSR modification

A new on-chip test generation technique based on the built-in self test (BIST) and deterministic test generation concepts has been proposed. Given a test set, the test patterns can be regenerated on the chip and applied to the circuit under test without the use of any external test equipments. A systematic procedure for the modification of a basic linear feedback shift register (LFSR) to realize the on-chip test generation hardware is given. Since the delay introduced by the modification of the LFSR is only two gate delays, at-speed testing of circuits is feasible. Experiments are conducted and test application time and hardware overhead are compared with a known test technique under the same fault coverage conditions. It is shown that both test cost and test application time can be decreased significantly by using the proposed technique.