analog output in vhdl

I want to see output of a vhdl program as analog wave from..Is it possible by using Xilinx-ISE?

If you meen "seeing" in hardware, you'll need a digital-to-analog conversion means. For low data rates, a pwm modulated pin with a low-pass can do. But involves additional logic. Some DevKits are equipped with DAC hardware, I think.

i mean not seeing in hardware..instead of digital output i need to see analog output..

Do you mean in simulation? Most simulators can display signed and unsigned signals as a waveform instead of hex, decimal and so on.

yes in simulation only we can see digital output as waveform..but we want to see analog output

I don't understand the question. VHDL and Xilinx ISE is not supporting analog signals. Can you give an example of the signal definition for the involved signal.

actually i want to find fft of a sine wave using vhdl..
for that i'd given some values of sine wave as input and i got output in digital form..
But i want the output in analog form...
What can i do for that?

The output of a FFT is a complex frequency spectrum, possibly converted to a scalar power spectrum. It's basically an array of magnitude values, covering the frequency range 0 to fs, number of points depending on the FFT resolution. How the "analog form" should look like?

Actually that i dont know..I'm doing my MTech project and my guide asked me to do this..
But i dont have any idea.

If you imagine a kind of spectrum analyzer display, the magnitude information (preferably in a logarithmic scale) can be send to a DAC, repeatedly with a sync signal or along with second X-axis analog signal and displayed by an oscilloscope. According to the FFT symmetry properties, you only need to display 0 to fs/2 for the real magnitude.

Now sir asked to do it on modelsim..
Any idea regarding that?
Thank you..

You can add analog signals in Modelsim. Search for "analog" in the user manual. I think it is simply a variation of formatting digital data. I don't think you will get it to display an FFT though!

Keith.

Assuming, that the data are output sequentially by the FFT core, the waveform display will work. That's what I suggested in post #4.

i want to simulate a program using modelsim..But i'm using an IPCore written in VHDL..So while simulating an error due to unisim library is coming.How can i eliminate this problem?

Depends on the exact error cause. The error message can be expected to give more information than yor post.

I guess the error is unisim library is not found.
Use "-L unisim" when you are compiling.

i'm compiling using isim..so no errors found..
But i want to simulate it using modelsim..Then error unisim library not found is coming..

Check this post...
Xilinx UNISIM/SIMPRIM libraries | Comp.Arch.FPGA | FPGARelated.com

post the exact error message... if this is not helpful

The error message is..

# ** Error: (vcom-42) Unsupported ModelSim library format for "C:\Modeltech_6.2c\win32\..\xilinx\vhdl\unisim". (Format: 3)
# ** Error: (vcom-42) Unsupported ModelSim library format for "C:\Modeltech_6.2c\win32\..\xilinx\vhdl\unisim". (Format: 3)
# ** Error: (vcom-42) Unsupported ModelSim library format for "C:\Modeltech_6.2c\win32\..\xilinx\vhdl\unisim". (Format: 3)
# ** Error: (vcom-11) Could not find C:\Modeltech_6.2c\win32\..\xilinx\vhdl\unisim.vcomponents.
# ** Error: fft.vhd(40): (vcom-1195) Cannot find expanded name: 'unisim.vcomponents'.
# ** Error: fft.vhd(40): Unknown record element "vcomponents".
# ** Error: (vcom-42) Unsupported ModelSim library format for "C:\Modeltech_6.2c\win32\..\xilinx\vhdl\unisim". (Format: 3)
# ** Error: (vcom-42) Unsupported ModelSim library format for "C:\Modeltech_6.2c\win32\..\xilinx\vhdl\unisim". (Format: 3)
# ** Error: (vcom-42) Unsupported ModelSim library format for "C:\Modeltech_6.2c\win32\..\xilinx\vhdl\unisim". (Format: 3)
# ** Error: (vcom-11) Could not find C:\Modeltech_6.2c\win32\..\xilinx\vhdl\unisim.vpkg.
# ** Error: fft.vhd(41): (vcom-1195) Cannot find expanded name: 'unisim.vpkg'.
# ** Error: fft.vhd(41): Unknown record element "vpkg".
# ** Error: fft.vhd(43): VHDL Compiler exiting
# ** Error: C:/Modeltech_6.2c/win32/vcom failed.

Hi all, I have the same error as Sajimol: (vcom-42) Unsupported ModelSim library format for "lvqsim" .(format 3)
I would like how you fix it, I'm using Altium designer and modelsim as simulator.
Help please, thanks.