System file I/O tasks

mcd = $fopen("file_name" [ , type ] );

$fopen


opens a disk file for writing, and returns a 32-bit unsigned integer multi-channel descriptor pointer to the file. It returns a zero if the file could not be opened for writing. In Verilog-2001 the

type

indicates how the file is to be opened. The “b” distinguishes a binary file from a text file:

$fclose(mcd);

$fclose


closes a disk file that was opened by $fopen.

$readmemb("file_name", memory_name [ , start_address [ , end_address ]] );
$readmemh("file_name", memory_name [ , start_address [ , end_address ]] );

$readmemb


and


$readmemh


initialize a memory array with the values from the file. The file must be an ASCII file with values represented in binary ($readmemb) or hexadecimal ($readmemh). The data values must be the same width as the memory array, and be separated by white spaces. The start and end address are hexadecimal numbers, even for $readmemb, preceded by @.

c = $fgetc(mcd);

$fgetc


reads a byte (a character) from the file.

ungetc(c, mcd);

$ungetc


inserts a specified character into a buffer specified by the file.

i = $fgets(str, mcd);

$fgets


reads a line from the file.

i = $fscanf(mcd, "text", signal, signal, ...);
i = $sscanf(str, "text", signal, signal, ...);

$fscanf


and


$sscanf


reads data and interprets the data according to a format.

i = $fread(reg_or_mem, mcd [ , start_address [ , end_address ]] );

$fread


reads


binary




data from the file.

i = $ftell(mcd)

$ftell


returns the offset from the beginning of the file.

i = $fseek(mcd, offset, operation);
i = $rewind(mcd);

$fseek


sets the position of the next input or output operation on the file.

$rewind


is the same as $fseek(0,0).

$fflush( [ mcd ] );

$fflush


writes any buffered output to the file.

i = $ferror(mcd, str);

$ferror


can be used to obtain more information about an error.

$swrite(output_reg, signal, signal, ...));
$sformat(output_reg, text", signal, signal, ...);

$swrite


and


$sformat


writes a string to a reg variable. $sformat interprets the string as a format string.

Example:
initial begin
  File = $fopen("Result.dat");
  if (!File)
    $display("Could not open \"result.dat\"");
  else begin
    $display(File, "Result is: %4b", A);
    $fclose(File);
  end
end

reg [7:0] Memory [15:0];
initial begin
  $readmemb("Stimulus.txt", Memory);
end