题解 | #根据状态转移写状态机-二段式#

和根据状态转移写状态机-三段式相比，就是将输出块和次态切换块合并。

`timescale 1ns/1ns

module fsm2(
	input wire clk  ,
	input wire rst  ,
	input wire data ,
	output reg flag
);

//*************code***********//
    parameter S0=0, S1=1, S2=2, S3=3, S4=4;
    reg [2:0] state, nstate;
    
    always@(posedge clk or negedge rst) begin
        if(~rst)
            state <= S0;
        else
            state <= nstate;
    end

    always@(*) begin
        if(~rst) begin
            nstate = S0;
            flag   = 0;
        end
        else
            case(state)
                S0: begin
                    nstate = data? S1: S0;
                    flag   = 0;
                end
                S1: begin
                    nstate = data? S2: S1;
                    flag   = 0;
                end
                S2: begin
                    nstate = data? S3: S2;
                    flag   = 0;
                end
                S3: begin
                    nstate = data? S4: S3;
                    flag   = 0;
                end
                S4: begin
                    nstate = data? S1: S0;
                    flag   = 1;
                end
                default: begin
                    nstate = S0;
                    flag   = 0;
                end
            endcase
    end
//*************code***********//
endmodule