$fread in SystemVerilog

SystemVerilog
, ,
1

Guys,
Trying to do something very simple. Obviously making a mistake. Newbie to SystemVerilog file I/O.

I have a binary data file called memFile.txt. It has only 1 line.
@0 11111111

I am trying to read this file using $fread (I know how to use $readmemb to do the same - but I want to use $fread).

Here’s my simple TB.

module fileIO;
  int    fd, status;
  logic [15:0] mem [0:15];
  logic [15:0] reg1;    
 
  initial begin
    fd = $fopen ("memFile.txt", "rb");
 
    //$readmemb ("memFile.txt", mem); //WORKS
    //display ("mem[0] = %b",status,mem[0]);
    
    status = $fread (reg1,fd); //DOES NOT WORK
    $display ("status = %0d reg1 = %b",status,reg1);
     
    $fclose(fd);
  end
endmodule

Simulation Output:
status = 2 reg1 = 0100000000110000

Can’t figure out the simulation output.
Thanks for your help.

2

In reply to a72:

This is the correct result. You have a text file with numbers formatted in a string of binary radix ASCII characters. The ASCII code for @ is 8’h40, and the ASCII code for 0 is 8’h30. So 16’h4030 is what $fread sees.

You probably want to use $fscanf(fd,"@%d %b", idx, reg1);
3

In reply to dave_59:

Dave, Thanks very much. Ok, that makes sense. I was trying to use the same file that I used for $readmemb.

What kind of file would $fread read in? Non-readable (as I call it) binary files?

4

In reply to a72:

$fread does not care whether a file is “human” readable or not—it’s just a series of bytes.