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How to read a text file in a VerilogA code

Alifa

 Hello every body!

I will greatly appreciate your help.

In order to test a serial DAC I need to input the DAC with serial bits ( any pattern like 01110001111), one bit at a clock cycle. So my text file (bit_sequence.txt) looks like this:

 1

0

 1

0

0

1

.

.

.

Basically, I want a VerilogA model that reads "bit_sequence.txt" and output one bit at a clock cycle to my DAC circuit. I tried the following code. It compiles with no error, but I can't see the above pattern in my simulation. Moreover, after running simulation, the bit_sequence.txt gets empty! :)

module fileReader_1output(out1, clk);
input clk;
output out1;
electrical out1, clk;

parameter real vtrans = 1.0;
parameter fileName = "~/bit_sequence.txt";

integer fileHandle;
integer decimal_output;
integer captured_data;

analog begin

    @ (initial_step)
        fileHandle = $fopen(fileName);
    @ (final_step)
        $fclose(fileHandle);
    @ (cross (V(clk) - vtrans,+1)) begin
                 
        decimal_output = $fscanf(fileHandle,"%d", captured_data);
        V(out1)<= decimal_output; //captured_data;    

     end
end

endmodule

Parents
  • skillUser

    Hi Alifa,

    When you use $fopen there is a second argument for the mode - I think that the default must be write (overwrite) and so you would need to specify read mode so that you don't clobber the file contents and so that you are able to read from the file.  I have not tried your example, but you may need to adjust the pattern to cope with possible spaces in the input file (your text above shows some preceeding space on some lines).

    Hopefully the first point is the only one that you need to account for and your code works after a minor adjustment. Good luck!

    Regards,

    Lawrence.

Reply
  • skillUser

    Hi Alifa,

    When you use $fopen there is a second argument for the mode - I think that the default must be write (overwrite) and so you would need to specify read mode so that you don't clobber the file contents and so that you are able to read from the file.  I have not tried your example, but you may need to adjust the pattern to cope with possible spaces in the input file (your text above shows some preceeding space on some lines).

    Hopefully the first point is the only one that you need to account for and your code works after a minor adjustment. Good luck!

    Regards,

    Lawrence.

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