Configure ModelSim simulation to display text

Question

Can I make ModelSim simulation to display text (rather than a numeric value) on a signal? I have a couple of state-machine states say,

localparam S_IDLE  = 2'b00; 
localparam S_START = 2'b01; 
localparam S_STOP  = 2'b10;

Is there a way to display S_IDLE for example, on a signal rather than 00? Thanks.

Answer 1

One thing you can do that is should work across all simulators is to create a signal that holds an ascii string, and then change the radix of that signal to ascii in the simulation window:

reg [8*8-1:0] mytextsignal;
always@(state) begin 
    case(state) 
        S_IDLE : mytextsignal = "  S_IDLE";
        S_START: mytextsignal = " S_START";
        S_STOP:  mytextsignal = "  S_STOP";
        default: mytextsignal = " UNKNOWN";
     endcase
 end

It should show up as readable text in the waveform viewer.