modelsim仿真时让状态机波形显示状态的名字

在使用Verilog编写有限状态机等逻辑的时候，状态机的各个状态通常以参数表示（如IDLE等）。当使用ModelSim仿真的时候，状态机变量在wave窗口中以二进制编码的形式显示，如下面所示，这种显示形式不是很直观，但我们可以使用ModelSim提供的命令将状态机变量以“文本”形式的参数名显示，从而有利于调试。

下面以一个实例来说明。

代码来源：http://www.cnblogs.com/oomusou/archive/2011/06/05/fsm_coding_style.html

源文件：

 1 /*
 2 (C) OOMusou 2011 http://oomusou.cnblogs.com
 3
 4 Filename    : simple_fsm_moore_3_always_best.v
 5 Synthesizer : Quartus II 8.1
 6 Description : 3 always block for moore fsm (BEST)
 7 Release     : Jun.05,2011 1.0
 8 */
 9
10 module simple_fsm (
11   clk,
12   rst_n,
13   w_i,
14   z_o
15 );
16
17 input  clk;
18 input  rst_n;
19 input  w_i;
20 output z_o;
21
22 parameter IDLE = 2‘b00;
23 parameter S0   = 2‘b01;
24 parameter S1   = 2‘b10;
25
26 reg [1:0] curr_state;
27 reg [1:0] next_state;
28 reg z_o;
29
30 // state reg
31 [email protected](posedge clk or negedge rst_n)
32   if (~rst_n) curr_state <= IDLE;
33   else        curr_state <= next_state;
34
35 // next state logic
36 [email protected](*)
37   case (curr_state)
38     IDLE    : if (w_i) next_state = S0;
39               else     next_state = IDLE;
40     S0      : if (w_i) next_state = S1;
41               else     next_state = IDLE;
42     S1      : if (w_i) next_state = S1;
43               else     next_state = IDLE;
44     default :          next_state = IDLE;
45   endcase
46
47 // output logic
48 [email protected](*)
49   case (curr_state)
50     IDLE    : z_o = 1‘b0;
51     S0      : z_o = 1‘b0;
52     S1      : z_o = 1‘b1;
53     default : z_o = 1‘b0;
54   endcase
55
56 endmodule

simple_fsm

测试文件：

 1 /*
 2 (C) OOMusou 2011 http://oomusou.cnblogs.com
 3
 4 Filename : simple_fsm_tb.v
 5 Simulator : ModelSim SE 6.3e + Debussy 5.4 v9
 6 Description : testbench for FSM
 7 Release : Jun.05,2011 1.0
 8  */
 9
10  module simple_fsm_tb;
11
12  reg clk = 1‘b1;
13  reg rst_n = 1‘b1;
14  reg w_i = 1‘b0;
15  wire z_o;
16
17  // clk
18  always #10 clk = ~clk;
19
20  event after_rst;
21
22  // rst_n
23  initial begin
24   #6; // 6ns
25   rst_n = 1‘b0;
26   #30; // 36ns
27   rst_n = 1‘b1;
28   ->after_rst;
29  end
30
31  // w_i
32  initial begin
33   @(after_rst);
34   repeat(2)@(posedge clk); // 60ns
35   w_i <= 1‘b1;
36   @(posedge clk); // 80 ns
37   w_i <= 1‘b0;
38   @(posedge clk); // 100 ns
39   w_i <= 1‘b1;
40   repeat(2)@(posedge clk); // 140 ns
41   w_i <= 1‘b0;
42   @(posedge clk); // 160 ns
43   w_i <= 1‘b1;
44   repeat(3)@(posedge clk); // 220 ns
45   w_i <= 1‘b0;
46 end
47
48 initial begin
49   $fsdbDumpfile("simple_fsm.fsdb");
50   $fsdbDumpvars(0, simple_fsm_tb);
51 end
52
53 simple_fsm u_simple_fsm (
54   .clk (clk),
55   .rst_n (rst_n),
56   .w_i (w_i),
57   .z_o (z_o)
58 );
59
60 endmodule

simple_fsm_tb.v

编写run.do文件

 1 vlib work
 2 vlog -novopt simple_fsm.v simple_fsm_tb.v
 3 vsim -voptargs=+acc work.simple_fsm_tb
 4 add wave *
 5 virtual type { {0x00 IDLE} {0x01 S0} {0x02 S1} } FSM_TYPE
 6 virtual function {(FSM_TYPE)/simple_fsm_tb/u_simple_fsm/curr_state} state1
 7 add wave u_simple_fsm/curr_state
 8 add wave -color pink /simple_fsm_tb/u_simple_fsm/state1
 9 virtual function {(FSM_TYPE)/simple_fsm_tb/u_simple_fsm/next_state} state2
10 add wave u_simple_fsm/next_state
11 add wave -color pink /simple_fsm_tb/u_simple_fsm/state2
12 run 1000ns

编写run.bat

1 vsim -do run.do

在文件夹内双击run.bat即可。如果双击该批处理文件程序没有运行，说明vsim命令没有执行，解决方案请参考http://www.cnblogs.com/ZcsTech/p/3495578.html

运行结果如下：