Simple FSM1(asynchronous reset)

This is a Moore state machine with two states, one input, and one output. Implement this state machine. Notice that the reset state is B.

This exercise is the same as fsm1s, but using asynchronous reset.

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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
        //声明了这是一个组合逻辑电路
        // State transition logic
        case(state)
            A:begin
                if(in) begin
                	next_state=A;
            	end
            	else begin
                	next_state=B;
            	end
            end
            B:begin
                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
        //实现异步复位
        // State flip-flops with asynchronous reset
        if(areset)begin
            state<=B;
        end
        else begin
            state<=next_state;
        end
    end

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