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Registered: ‎01-22-2013

shift register to xfft problem



I am trying to connect a virtex-6 system monitor module to a shift register, which will then transport the data to an xfft 7.1 module, for the fft to be done. The problem is, even though the shift register works perfectly when simulating alone, which means it shifts the data given from the simulation file, when i try to simulate the whole thing, with a testbench on xfft 7.1 , the results from the shift register are invalid (e.g x00x0x00xx instead of 1001010011, always x's are at 1's places), which makes the xk output invalid too. I connected the shiftreg to the xfft with the line

  shiftreg( ,xn_re);


as the second port is the output of the shiftreg, and xn_im=0.


the core generator options are:


-256 points

-Target Clk frequency and  Data Throughput is set to 550 MHz and KSps respectively

-10-bit phase and input width

-Fixed point format, scaled with truncation rounding mode

-CLB logic

-4-multiplier structure

-1 stage using block RAM


The simulation wave is attached.


As i am new to verilog, i'm sure there's something i can't see it's wrong, but i don't know what it is, so please help :)

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