Why do I get the a.out 1:syntax error when I run Icarus Verilog simulation?

Question

module round_robbin
    #(
        parameter   UNIT = 3,
        parameter   CH1_WT = 1,
        parameter   CH2_WT = 1,
        parameter   CH3_WT = 1,
        parameter   CH4_WT = 1,
        parameter   ADDR_WIDTH = 8,
        parameter   DATA_WIDTH = 8,
        parameter   CHANNELS = 4
    )(
    input                         i_rt_lt,
    input                         i_clk,
    input                         i_rst_,
    input       [ADDR_WIDTH:1]    i_addr  [CHANNELS:1],
    input       [DATA_WIDTH:1]    i_data  [CHANNELS:1],
    input       [CHANNELS:1]      i_wr,
    input       [CHANNELS:1]      i_rd,
    output reg  [ADDR_WIDTH:1]    o_addr,
    output reg  [DATA_WIDTH:1]    o_data,
    output reg                    o_wr,
    output reg                    o_rd
    );
    typedef enum logic [$clog2(CHANNELS)-1:0] {  CH1 = 2'b00,
                                CH2 = 2'b01,
                                CH3 = 2'b10,
                                CH4 = 2'b11} fsm_states;
    fsm_states ps, ns;
    reg [6:0] ch1_cnt;
    reg [6:0] ch2_cnt;
    reg [6:0] ch3_cnt;
    reg [6:0] ch4_cnt;
always@(posedge i_clk or negedge i_rst_)    begin
    if(!_rst_)
        ps <= CH1;
    else
        ps <= ns;
end

always@(*)  begin
    case(ps)
        CH1:begin
            if((ch1_cnt == (CH1_WT * UNIT)) && i_rt_lt)
                ns = CH2;
            else if((ch1_cnt == (CH1_WT * UNIT)) && !i_rt_lt)
                ns = CH4;
            else
                ns = CH1;
        end
        CH2:begin
            if((ch2_cnt == (CH2_WT * UNIT)) && i_rt_lt)
                ns = CH3;
            else if((ch2_cnt == (CH2_WT * UNIT)) && !i_rt_lt)
                ns = CH1;
            else
                ns = CH2;
        end
        CH3:begin
            if((ch3_cnt == (CH3_WT * UNIT)) && i_rt_lt)
                ns = CH4;
            else if((ch3_cnt == (CH3_WT * UNIT)) && !i_rt_lt)
                ns = CH2;
            else
                ns = CH3;
        end
        CH4:begin
            if((ch4_cnt == (CH4_WT * UNIT)) && i_rt_lt)
                ns = CH1;
            else if((ch4_cnt == (CH4_WT * UNIT)) && !i_rt_lt)
                ns = CH3;
            else
                ns = CH4;
        end
    endcase
end

always@(*)  begin
    case(ps)
        CH1:begin
            o_rd = i_rd[1];
            o_wr = i_wr[1];
            o_data = i_data[1];
            o_addr = i_addr[1];
        end
        CH2:begin
            o_rd = i_rd[2];
            o_wr = i_wr[2];
            o_data = i_data[2];
            o_addr = i_addr[2];
        end
        CH3:begin
            o_rd = i_rd[3];
            o_wr = i_wr[3];
            o_data = i_data[3];
            o_addr = i_addr[3];
        end
        CH4:begin
            o_rd = i_rd[4];
            o_wr = i_wr[4];
            o_data = i_data[4];
            o_addr = i_addr[4];
        end
    endcase
end

always@(posedge clk)  begin
    case(ps)
        CH1:begin
            ch1_cnt = ch1_cnt + 1;
            ch2_cnt = 7'd0;
            ch3_cnt = 7'd0;
            ch4_cnt = 7'd0;
        end
        CH2:begin
            ch1_cnt = 7'd0;
            ch2_cnt = ch2_cnt + 1;
            ch3_cnt = 7'd0;
            ch4_cnt = 7'd0;
        end
        CH3:begin
            ch1_cnt = 7'd0;
            ch2_cnt = 7'd0;
            ch3_cnt = ch3_cnt + 1;
            ch4_cnt = 7'd0;
        end
        CH4:begin
            ch1_cnt = 7'd0;
            ch2_cnt = 7'd0;
            ch3_cnt = 7'd0;
            ch4_cnt = ch4_cnt + 1;
        end
    endcase
end
endmodule

module round_robbin_tb;
        parameter   UNIT = 6;
        parameter   ADDR_WIDTH = 3;
        parameter   DATA_WIDTH = 3;
        parameter   CHANNELS = 4;
        reg i_rt_lt;
        reg i_clk;
        reg i_rst_;
        reg [ADDR_WIDTH:1]    i_addr  [CHANNELS:1];
        reg [DATA_WIDTH:1]    i_data  [CHANNELS:1];
        reg [CHANNELS:1]      i_wr;  
        reg  [CHANNELS:1]      i_rd; 
        wire [ADDR_WIDTH:1]    o_addr;
        wire  [DATA_WIDTH:1]    o_data;
        wire                    o_wr;
        wire                    o_rd; 
    round_robbin #(.UNIT(UNIT),
               .ADDR_WIDTH(ADDR_WIDTH),
               .DATA_WIDTH(DATA_WIDTH),
               .CHANNELS(CHANNELS)
              )DUT (i_rt_lt,
             i_clk,
             i_rst_,
             i_addr,
             i_data,
             i_wr,
             i_rd,
             o_addr,
             o_data,
             o_wr,
             o_rd
              );
    always i_clk = #1 ~i_clk;
        initial begin
        $dumpfile("round_robbin.vcd");
        $dumpvars("0,round_robbin_tb");
        i_rt_lt = 0;
        i_clk = 0;
        i_rst_ = 1;
        i_addr[0]=2;
        i_addr[1]=4;
        i_addr[2]=5;
        i_addr[3]=6;
        i_data[0]=4;
        i_data[1]=6;
        i_data[2]=5;
        i_data[3]=1;
        i_wr=$urandom;
        i_rd=$urandom;
        #5;
        i_rst_=0;
        #3;
        i_rst_=1;
        #100;
        $finish;
    end
endmodule

iverilog -g2005-sv -pfileline=1 -E round_robbin.sv round_robbin_tb.sv -Wall

I have no errors in using the above command.

After that, I used vvp a.out, then I get this error message:

a.out 1:syntax error

Can anyone help me?

Answer 1

You should not use the -E option on the iverilog command line. That prevents iverilog from creating the compiled version of the Verilog source code required for input to the vvp simulator command.

When using -E, the a.out output file is simply a copy of your 2 input Verilog files run through the preprocessor. It does not compile the Verilog code into the binary file format required by the vvp command. You didn't receive any error with the iverilog command because the preprocessor did not find any errors with the code. However, you do get the error when running the vvp command because the a.out file is the wrong format.

Refer to the Icarus Verilog documentation for details about the -E option.

When I don't use -E, I get plenty of messages from iverilog:

iverilog -g2005-sv -pfileline=1  round_robbin.sv round_robbin_tb.sv -Wall
round_robbin.sv:35: error: Unable to bind wire/reg/memory `_rst_' in `round_robbin_tb.DUT'
round_robbin.sv:35: error: Unable to elaborate condition expression.
round_robbin.sv:83: warning: @* is sensitive to all 4 words in array 'i_data'.
round_robbin.sv:84: warning: @* is sensitive to all 4 words in array 'i_addr'.
round_robbin.sv:89: warning: @* is sensitive to all 4 words in array 'i_data'.
round_robbin.sv:90: warning: @* is sensitive to all 4 words in array 'i_addr'.
round_robbin.sv:95: warning: @* is sensitive to all 4 words in array 'i_data'.
round_robbin.sv:96: warning: @* is sensitive to all 4 words in array 'i_addr'.
round_robbin.sv:101: warning: @* is sensitive to all 4 words in array 'i_data'.
round_robbin.sv:102: warning: @* is sensitive to all 4 words in array 'i_addr'.
round_robbin.sv:107: error: Unable to bind wire/reg/memory `clk' in `round_robbin_tb.DUT'
posedge clk
round_robbin_tb.sv:40: warning: ignoring out of bounds l-value array access i_addr[0].
round_robbin_tb.sv:44: warning: ignoring out of bounds l-value array access i_data[0].
4 error(s) during elaboration.

To fix the error messages, in the round_robbin module, change _rst_ to i_rst_, and change clk to i_clk.

I get another error when I run the simulation. You must remove the quotes from the $dumpvars line:

    $dumpvars(0,round_robbin_tb);