2. 2
File Output
Oct 8 2012
• Opening a file
• $fopen is used to open a file.
• Syntax <file_handle> = $fopen (“<name of
file>”);
• The task $fopen returns a 32-bit value called
multichannel descriptor.
• Only one bit is set in a multichannel descriptor.
• The standard output is always open.
• It has a multichannel descriptor value = 32’d1Lecture 16
4. 4
Writing to files
Oct 8 2012
• The system tasks $fdisplay, $fmonitor,
$fwrite, and $fstrobe are used to write to files.
• similar in syntax to regular system tasks
$display, $monitor, etc., but they provide
the additional capability of writing to files.
•Syntax $fdisplay (<file_descriptor>, p1, p2, ….pn);
$fmonitor (<file_descriptor>, p1, p2, ….pn);
• p1, p2,.. pn can be variables, signal names, or
quoted strings.
Lecture 16
6. 6
Closing files
Oct 8 2012
• Files can be closed with the system task $fclose.
• Syntax $fclose <file_handle>);
• A file cannot be written to once it is closed.
• The corresponding bit in the multichannel
descriptor is set to 0.
Lecture 16
7. 7
Displaying Hierarchy
Oct 8 2012
• Hierarchy at any level can be displayed by means
of the %m option in any of the display tasks,
$display, $write task, $monitor, or
$strobe task.
• When multiple instances of a module execute the
same Verilog code, the %m option will distinguish
from which module instance the output is coming.
• No argument is needed for the %m option in the
display tasks.
Lecture 16
