File Handling in Verilog

The Verilog language has a rich set of system functions to write files ($fdisplay, $fwrite, etc.) but only reads files with a single, fixed format ($readmem). In the past if you wanted to read a file that was not in $readmem format, you would have to learn the Programming Language Interface (PLI) and the C language, write C code to read the file and pass values into Verilog, then debug the combined C and Verilog code. In addition, the Verilog is limited to 32 open files at a time.

To Write into a file -> 

module tb;

integer fl1;

initial begin

  fl1 = $fopen("file.xyz");

  

  forever  begin

    @(posedge clk)

    $fdisplay(fl1, "value to print = %h", value);

 end

 $fclose(fl1);

end 

endmodule

Read a file in Verilog.

file = $fopen("filename");

Reading data for per clock cycle ->  (In System Verilog)

integer data_file ; // file handler
integer scan_file ; // file handler
logic signed [21:0] capture_data;

`define NULL 0

 initial begin
   data_file = $fopen("data_file.txt", "r");
   if (data_file == `NULL) begin
     $display("data_file handle was NULL");
     $finish;
  end
end

always @(posedge clk) begin
  scan_file = $fscanf(data_file, "%d\n", capture_data);
  if (!$feof(data_file)) begin //use capture_data;
 end
end

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