题解 | #Johnson Counter#

开始这么写：

`timescale 1ns/1ns

module JC_counter(
   input                clk ,
   input                rst_n,
 
   output reg [3:0]     Q  
);
    always@(posedge clk or negedge rst_n)begin
        if(!rst_n) Q <= 'd0;
        else if(!Q[0]) Q <= {1'b1, Q[3 : 1]};
        else Q <= {1'b0, Q[3 : 1]};
    end
endmodule

看了答案这么写

`timescale 1ns/1ns

module JC_counter(
   input                clk ,
   input                rst_n,
 
   output reg [3:0]     Q  
);
    always@(posedge clk or negedge rst_n)begin
        if(!rst_n) Q <= 'd0;
        else Q <= {~Q[0], Q[3 : 1]};
    end
endmodule