call FFT function from dsplib of vc5510

hi,
i would like to ask is this the correct way to call FFT function from
dsplib of vc5510 

           rfft(sinetable,256,SCALE);

currently i am generating a 12 cycle sine waveform to test this FFT
function.

how should i configure so that i can get the FFT display under the single
time display type.