题解 | #移位运算与乘法#

`timescale 1ns/1ns
module multi_sel(
input [7:0]d ,
input clk,
input rst,
output reg input_grant,
output reg [10:0]out
);
//*************code***********//

reg     [1:0]   cnt;
reg     [7:0]   d_reg;

always@(posedge clk or negedge rst)
    if(!rst)
        d_reg <= 8'b0;
    else if(cnt == 2'd0)
        d_reg <= d;
    else
        d_reg <= d_reg;

always@(posedge clk or negedge rst)
    if(!rst)
        cnt <= 2'd0;
    else if(cnt == 2'd3)
        cnt <= 2'b0;
    else
        cnt <= cnt + 1'b1;

always@(posedge clk or negedge rst)
    if(!rst)
        input_grant <= 1'b0;
    else if(cnt == 2'd0)
        input_grant <= 1'b1;
    else
        input_grant <= 1'b0;

always@(posedge clk or negedge rst)
    if(!rst)
        out <= 11'b0;
    else
        case(cnt)
        2'd0    :   out <= d;	//d_reg打一拍，不能用d_reg
        2'd1    :   out <= (d_reg << 1) + d_reg;
        2'd2    :   out <= (d_reg << 3) - d_reg;
        2'd3    :   out <= (d_reg << 3);
        default :   out <= 11'b111_1111_1111;
        endcase


//*************code***********//
endmodule