4位乘法器的实现

• 组合逻辑实现

module mult4(
       input  wire [3:0] a,
	   input  wire [3:0] b,
	   output reg  [7:0] y
	   );
	   integer i;
	   reg [7:0] bp;
	   reg [7:0] pv;
	always @(*)
	  begin
	    pv=8'b00000000;
		bp={4'b0000,b};
	    for (i=0;i<4;i=i+1)
		  begin
		    if(a[i]==1)
			  pv=pv+bp;
			  bp={bp[6:0],1'b0};
		  end
		y=pv;
	  end
endmodule

• 时序逻辑

module multi_4bits_pipelining(mul_a, mul_b, clk, rst_n, mul_out);
    
    input [3:0] mul_a, mul_b;
    input       clk;
    input       rst_n;
    output [7:0] mul_out;

    reg [7:0] mul_out;

    reg [7:0] stored0;
    reg [7:0] stored1;
    reg [7:0] stored2;
    reg [7:0] stored3;

    reg [7:0] add01;
    reg [7:0] add23;

    always @(posedge clk or negedge rst_n) begin
        if(!rst_n) begin
            mul_out <= 0;
            stored0 <= 0;
            stored1 <= 0;
            stored2 <= 0;
            stored3 <= 0;
            add01 <= 0;
            add23 <= 0;
        end
        else begin
            stored0 <= mul_b[0]? {4'b0, mul_a} : 8'b0;
            stored1 <= mul_b[1]? {3'b0, mul_a, 1'b0} : 8'b0;
            stored2 <= mul_b[2]? {2'b0, mul_a, 2'b0} : 8'b0;
            stored3 <= mul_b[3]? {1'b0, mul_a, 3'b0} : 8'b0;

            mul_out<= stored1 + stored0+stored3 + stored2;
            


        end
    end