verilog四指令cpu代码

以下是一个简单的Verilog代码实现四指令CPU：

module cpu (
  input clk,
  input reset_n,
  input [7:0] instr,
  output reg [7:0] dout
);

reg [7:0] reg_a;
reg [7:0] reg_b;
reg [7:0] reg_c;
reg [7:0] reg_d;
reg [7:0] imm;

always @(posedge clk) begin
  if (~reset_n) begin
    reg_a <= 8'b0;
    reg_b <= 8'b0;
    reg_c <= 8'b0;
    reg_d <= 8'b0;
    imm <= 8'b0;
    dout <= 8'b0;
  end else begin
    case (instr)
      8'h00: begin // ADD
        dout <= reg_a + reg_b;
      end
      8'h01: begin // SUB
        dout <= reg_a - reg_b;
      end
      8'h02: begin // MOV
        dout <= reg_b;
      end
      8'h03: begin // LDI
        dout <= imm;
      end
      8'h04: begin // STO
        reg_c <= dout;
      end
      8'h05: begin // LD
        dout <= reg_c;
      end
      8'h06: begin // JMP
        reg_d <= imm;
      end
      8'h07: begin // JZ
        if (dout == 0) begin
          reg_d <= imm;
        end
      end
      8'h08: begin // JNZ
        if (dout != 0) begin
          reg_d <= imm;
        end
      end
    endcase
    reg_b <= reg_a;
    reg_a <= dout;
    imm <= instr[7:0];
  end
end

always @(posedge clk) begin
  if (~reset_n) begin
    dout <= 8'b0;
  end else begin
    case (instr)
      8'h00, 8'h01, 8'h02, 8'h03, 8'h04, 8'h06, 8'h07, 8'h08: begin
        dout <= dout;
      end
      8'h05: begin
        dout <= reg_c;
      end
    endcase
  end
end

endmodule

该CPU支持以下四条指令：

1. ADD：将寄存器A和寄存器B的值相加，并将结果存储在寄存器A中。
2. SUB：将寄存器A和寄存器B的值相减，并将结果存储在寄存器A中。
3. MOV：将寄存器B的值复制到寄存器A中。
4. LDI：将立即数的值存储在输出寄存器中。