stuck with plotting FFT of chirp signal in simulink

hello ,

       I want to plot fft of chirp signal. I am using chirp signal block from simulink and connected to zero order hold and then FFT spectrum scope but when i am running simulation , th display of spectrum scope not displaying anything.

 I have put buffer size 256 , then FFT length 256 and spectrum type Two sided.

any one is having idea what is wrong

[Navan Ruthramoorthy]

How long did you run your model? Try increasing "Samples per frame" setting in Chirp block.