Honored Contributor
Honored ContributorHi,
There are a few issues in the code. 1. You cannot use initial blocks and $display tasks in RTL code for synthesis as these constructs are non-synthesizable . These are used only for simulation 2. The code does not have a reset value or initial value. Use an asynchronous reset input and in the always block check for its negedge. When reset is asserted, initialize the count and output to '0'. 3. The reason why led is always 0, is due to the fact that for the first case item (case 0) it will get the value from the parameter. For the next case items (case 1,2,3,4).. You are left shifting the value in the register which is always at 0. This is due to the fact that, after the case is hit, its value will get updated outside the always block. So the next time the code comes back to the case and hits the next one, the value of the led variable is 0. The previous value of led variable is not stored. You can accomplish this by modifying the default condition..
default : led <= led;
