Using Tasks to Blink an LED in Verilog

I am using Tasks for the first time in Verilog in an attempt to achieve code reuse. I have two tasks, led_on and led_off. I can light up an LED or turn it off with these tasks individually. The problem is when I attempt to run led_blink, a task which combines led_on and led_off tasks, the output led remains undefined until the blink task finishes, leaving the led state matching the last call within the function (led_off, in my example below).

Here's my led_on and led_blink tasks, as well as my task call:

// LED On
task led_on;
  inout  led;

  begin
    #10000
    led = 1;
  end
endtask

// LED Blink
task led_blink;
  inout led;

  begin
    led_on  (led);
    led_off (led);
    led_on  (led);
    led_off (led);
  end
endtask

// Task Call(s)
initial begin
  led_blink     (led_out);
end

Solution

I suspect you are running into trouble with the inout ports. I have simplified your code by using a reg named led which can be set and cleared in your tasks:

module tb;

reg led;

task led_on;
    #10000 led = 1;
endtask

task led_off;
    #10000 led = 0;
endtask

task led_blink;
    begin
        led_on ;
        led_off;
        led_on ;
        led_off;
    end
endtask

initial begin
    $monitor($time, " ", led);
    led_blink;
end

endmodule

Outputs: