FFT butterfly network design for easy testing

The authors consider offline testing and easily testable design of butterfly networks for fast Fourier transform. The butterfly networks are shown to be testable with 32 patterns using a design-for-testability technique based on the M-testability conditions. The functional-level cell-fault model is assumed, and the fault coverage for combinational single cell faults is 100%. A higher-level fault model-the module-fault model-is also discussed. A novel input-assignment technique based on the functional bijectivity property of the butterfly modules is presented for discovering faults other than cell faults (e.g., interconnection faults)