SYSTEMS AND METHODS FOR SIGNATURE CIRCUITS

Signature circuits are used during testing of an integrated circuit. Test vectors are applied as inputs to a circuit under test. A signature circuit stores a “signature” for the circuit under test based on a combination of signals from the circuit under test in response to test vectors and a previous stored state of the signature register. The value contained in the signature register at the end of the test is the signature. A fault-free circuit generates a particular signature for the applied test vectors. Faults can be determined by detecting variances from the expected signature. In one embodiment, the signature circuit uses a combination of two error detection codes.