Question

总和：状态机名为“ WaitS2 ”的部件仅会使“ 计数”增加一次。

我正在尝试在 systemverilog 中控制超声传感器 HC-SR04 。正如我在数据表中看到的那样，此传感器创建一个信号“ 触发”，该信号创建声音，并且在生成声音传感器后创建一个逻辑“ 回声”，我需要对时间，以便我创建可以在代码中看到的状态机，但是问题是count ++的运行不尽人意，无论回声信号有多长，它只能递增一次count变量

我使用了另一个来自互联网的称为32位加法器的模块，该模块没有做任何更改。我将所有语句更改为不起作用的非阻塞语句。我什至尝试将count++更改为count = count + 1无效

module sensorFSM(
    input logic echo , clk ,reset, 
    output logic trig,
    output logic[31:0] distance,
    output logic[1:0] presentState
    );
    /*typedef enum logic[1:0] {BeginS , WaitS , ReturnS } states;
    states presentState , nextState;
    */
    logic[31:0] count , count1; 
    logic[1:0] BeginS , WaitS, WaitS2 , ReturnS  , nextState;
    assign BeginS = 2'b00;
    assign WaitS = 2'b01; 
    assign WaitS2 = 2'b10;
    assign ReturnS = 2'b11; 

    // clk and state change
    always_ff @( posedge clk )
        begin
            if ( reset == 1'b1 )
            presentState <= BeginS;
            else
            presentState <= nextState;
        end

    // real state changes    
    always_comb 
        begin            
            case(presentState)           
            BeginS:
                begin
                    trig = 1'b1;
                    count = 32'b0;
                    nextState = WaitS;
                end
            WaitS:
                begin
                    trig = 1'b0;
                    distance = 32'b0;
                    //#5000;
                    nextState = WaitS2;
                end
            WaitS2:
                begin
                    if( echo  == 1 )
                      begin
                        if ( count < 24'b101100111000000100100000 )
                            begin 
                            // here is the problem count is only incrementing 
                            //once
                                count++;                               
                                nextState = WaitS2; 
                            end 
                         else 
                            begin
                                distance = count;
                                nextState = BeginS;
                            end 
                      end
                    else // echo == 0   
                        begin
                            nextState = ReturnS;
                        end
                   end 
            ReturnS:
                begin
                    //count =  count / 1470;
                    distance = count;
                    nextState = BeginS;
                end
            default:
                nextState = BeginS;
            endcase
         end  
endmodule

我希望模拟的计数大约为1 miliion，但它始终会输出1，但是我可以看到，当回波也处于活动状态时，会长时间存在名为“ WaitS2”的状态

Answer 1

您在count++;中使用always_comb创建了一个异步反馈循环。您需要注册count。

此外，trig和distance当前是级别敏感的锁存器。 distance必须失败。 trig可以写成纯粹的组合逻辑，但是由于它是输出，因此我强烈建议将其设为触发器，以消除输出毛刺的出现。

always_ff @( posedge clk )
    begin
      if ( reset == 1'b1 ) begin
        presentState <= BeginS;
        trig <= 0; // <-- reset
        distance <= 0; // <-- reset
        count <= 0; // <-- reset
      end else begin
        presentState <= nextState;
        trig <= next_trig; // <-- flop trig
        distance <= next_distance; // <-- flop distance
        count <= next_count; // <-- flop count
      end
    end

// real state changes    
always_comb 
    begin
      next_trig = trig; // <-- default value is flopped value
      next_distance = distance; // <-- default value is flopped value
      next_count = count; // <-- default value is flopped value
        case(presentState)           
        BeginS:
            begin
                //trig = 1'b1; // <-- is now a flop assigned in always_ff
                //count = 32'b0; // <-- is now a flop assigned in always_ff
                next_trig = 1'b1; // <-- update value
                next_count = 32'b0; // <-- update value
                nextState = WaitS;
            end
        WaitS:
            // ... replace trig/distance with next_trig/next_distance in here ...
        WaitS2:
            begin
              // ...
              //count++;  // <-- NOPE would be asynchronous feedback
              next_count = count + 1; // <-- synchronous increment
              // ...
            end
        ReturnS:
            //  ... replace distance with next_distance in here ...
        default:
            nextState = BeginS;
        endcase
     end

Systemverilog Vivado中的增量操作未按预期工作

1 个答案: