HDLbits有限状态机写法

Question

HDLbits里的状态机写法，下面这两种写法有什么不一样吗，为什么第一种就仿真结果错误

module top_module(
    input clk,
    input areset,    // Asynchronous reset to state B
    input in,
    output out);//  

    parameter A=0, B=1; 
    reg state, next_state;

    always @(*) begin    // This is a combinational always block
        // State transition logic
        case(state)
            A:begin
                if(in)begin
                next_state = A;
                out = 1'b0;
             end
               else begin
                next_state = B;
                out = 1'b1;
               end
            end
            B:begin
                if(in) begin
                next_state = B;
                out = 1'b1;
               end
               else begin
                next_state = A;
                out = 1'b0;
               end
            end
        endcase
    end

    always @(posedge clk, posedge areset) begin    // This is a sequential always block
        // State flip-flops with asynchronous reset
        if(areset)
            state <= B;
        else
            state <= next_state;
    end

    // Output logic
    //assign out = (state == B);// assign out = (state == ...);

endmodule

module top_module(
    input clk,
    input areset,    // Asynchronous reset to state B
    input in,
    output out);//  

    parameter A=0, B=1; 
    reg state, next_state;

    always @(*) begin    // This is a combinational always block
        case(state)
            A:begin
                if(in == 1'b1)begin
                    next_state <= A;
                end
                else begin
                    next_state <= B;
                end
            end
            B:begin
                if(in == 1'b1)begin
                    next_state <= B;
                end
                else begin
                    next_state <= A;
                end
            end
        endcase
    end

    always @(posedge clk, posedge areset) begin    // This is a sequential always block
        if(areset)begin
            state <= B;
        end
        else begin
            state <= next_state;
        end
    end

    // Output logic
    assign out = (state == B);

endmodule

Answer 1

第一种代码中
out 的值与 in 有逻辑关联，这是不对的
可以按如下更改，综合后的结果应该和第二种代码一样

module top_module(
    input clk,
    input areset,    // Asynchronous reset to state B
    input in,
    output out);//  
 
    parameter A=0, B=1; 
    reg state, next_state;
 
    always @(*) begin    // This is a combinational always block
        // State transition logic
        case(state)
            A:begin
                out = 1'b0;
                if(in)begin
                next_state = A;
                end
                else begin
                next_state = B;
               end
            end
            B:begin
                out = 1'b1;
                if(in) begin
                next_state = B;
                end
                else begin
                next_state = A;
                end
            end
        endcase
    end
 
    always @(posedge clk, posedge areset) begin    // This is a sequential always block
        // State flip-flops with asynchronous reset
        if(areset)
            state <= B;
        else
            state <= next_state;
    end
 
    // Output logic
    //assign out = (state == B);// assign out = (state == ...);
 
endmodule