ALtera FFT Outputs in SignalTapII

Altera_Forum · ‎05-17-2017

Hello,

I'm using an Alter 1024-point FFT IP (burst) and after implementing it I used SignalTapII for the FFT outputs acquisition. Now, I want to plot these output values using MATLAB but I'm a little confused about the format of these outputs. For testing I used 32-bit real input, all ones, and the imaginary is fixed to zero.

How are the real and exponent outputs represented; are they just decimal, signed or two's complement signed? How can I correctly plot these outputs?

Thanks

Altera_Forum · ‎05-18-2017

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Hello,

I'm using an Alter 1024-point FFT IP (burst) and after implementing it I used SignalTapII for the FFT outputs acquisition. Now, I want to plot these output values using MATLAB but I'm a little confused about the format of these outputs. For testing I used 32-bit real input, all ones, and the imaginary is fixed to zero.

How are the real and exponent outputs represented; are they just decimal, signed or two's complement signed? How can I correctly plot these outputs?

Thanks

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altera fftcore if set to block floating point then output = fft_output * 2^(-exponent)

Re/im data & exponent are all signed.

signed = decimal = 2's complement...usually