After the choice for input bit width and twiddle factors is made with no scaling, which gives acceptable SNR or root mean square (RMS) error at the output of fixed point 1-D SSR FFT, you can start to experiment with the choice of scaling modes. Three different scaling modes are available with 1-D SSR FFT. The recommended strategy is to start with SSR_FFT_NO_SCALING. If there is an acceptable SNR/RMS error at the output, switch to SSR_FFT_GROW_TO_MAX_WIDTHi. If there is still an acceptable SNR/RMS error, switch to SSR_FFT_SCALE and observe the SNR/RMS again if it is acceptable keep using SSR_FFT_SCALE, otherwise revert back to another mode which gives acceptable SNR/RMS error at the output.