The data type to the FFT is controlled by the TT_DATA template parameter. This can take one of three choices: cint16, cint32, or cfloat. This selection applies to both input data and output data. The template parameter TT_TWIDDLE can take one of three values, cint32, cint16 or cfloat. However, TT_DATA and TT_TWIDDLE must both be integer types or must both be cfloat.