always @(posedge clk)
        begin
                case (state)
-               0:
+               0: // initialize
                        begin
                                if (cur_max_val >= ({1'b0, adc_d} + threshold))
                                        state <= 2;
                                else if (adc_d <= cur_min_val)
                                        cur_min_val <= adc_d;                                   
                        end
-               1:
+               1: // high phase
                        begin
                                if (cur_max_val <= adc_d)
                                        cur_max_val <= adc_d;
                                        max_val <= cur_max_val;
                                end
                        end
-               2:
+               2: // low phase
                        begin
                                if (adc_d <= cur_min_val)
                                        cur_min_val <= adc_d;