题解 | 使用握手信号实现跨时钟域数据传输

`timescale 1ns/1ns
module data_driver(
	input clk_a,
	input rst_n,
	input data_ack,
	output reg [3:0]data,
	output reg data_req
	);
    reg [2:0] ack_reg;
    reg [2:0] count;
    //跨时钟域，此处打2拍避免亚稳态
    always@(posedge clk_a or negedge rst_n) begin
        if(!rst_n)
          ack_reg <= 3'b0;
        else
          ack_reg <= {ack_reg[1:0],data_ack};
        end
    //ack上升沿
    assign ack_posedge = !ack_reg[2] && ack_reg[1];

    always@(posedge clk_a or negedge rst_n) begin
        if(!rst_n)
            count <= 3'b0;
        else if(ack_posedge)
            count <= 3'b0;
        else
            count <= count + 1'b1;
    end

    always@(posedge clk_a or negedge rst_n) begin
        if(!rst_n) begin
            data <= 3'b000;
            data_req <= 1'b0;
        end
        else if(count == 3'b100)
            data_req <= 1'b1;
        else if(ack_posedge) begin
            data_req <= 1'b0;
            data <= data + 1'b1;
        end
    end
endmodule

module data_receiver(
    input clk_b,
    input rst_n,
    input data_req,
    input [3:0] data,
    output reg data_ack

);
    reg [3:0] data_reg;
    reg [2:0] req_reg;
    always@(posedge clk_b or negedge rst_n) begin
        if(!rst_n)
          req_reg <= 3'b0;
        else
          req_reg <= {req_reg[1:0],data_req};
        end
    //req上升沿
    assign req_posedge = !req_reg[2] && req_reg[1];

    always@(posedge clk_b or negedge rst_n) begin
        if(!rst_n) begin
            data_ack <= 1'b0;
        end
        else if(req_reg[1]) begin
            data_ack <= 1'b1;
        end
        else begin
        	data_ack <= 1'b0;
        end
    end

    always@(posedge clk_b or negedge rst_n) begin
        if(!rst_n) begin
            data_reg <= 4'b0;
        end
        else if(req_posedge) begin
            data_reg <= data;
        end
    end   
endmodule