TESTING A FEEDBACK SHIFT-REGISTER

A Feedback Shift-Register (FSR) enabling improved testing, e.g., Built-In Self-Tests (BIST), is provided. Each cell of the FSR may either be an observable cell, associated with a non-trivial feedback function implemented by a combinational logic circuit, or a controllable cell, having an associated state variable which belongs to the dependence set of exactly one of the non-trivial feedback functions. Each controllable cell is provided with a multiplexer for selecting either a predecessor cell of the controllable cell or a test value as input. Thus, the sequential circuit of the FSR in an embodiment is tested using tests for combinational logic. The disclosed test procedures utilize a minimal set of test vectors and allow detection of all single stuck-at faults in the FSR. The resulting dynamic power dissipation during test can be considerably less than known BIST designs.