if_single_decode.v

来自「《设计与验证VerilogHDL》源码实例 和 Verilog规范」· Verilog 代码 · 共 31 行

// Use case statement to build decode circuit without prior

`timescale 1ns/1ps
module if_single_decode (addr_H, CS1, CS2, CS3, CS4);
input  [2:0] addr_H;
output       CS1, CS2, CS3, CS4;
reg    [3:0] CS_bus;

parameter CHIP1 = 3'b100,
          CHIP2 = 3'b101,
          CHIP3 = 3'b010,
          CHIP4 = 3'b011;

     always @ (addr_H)
              if (addr_H == CHIP1)
                  CS_bus = 4'b0111;
              else if (addr_H == CHIP2)
                  CS_bus = 4'b1011;
              else if (addr_H == CHIP3)
                  CS_bus = 4'b1101;
              else if (addr_H == CHIP4)
                  CS_bus = 4'b1110;
              else
                  CS_bus = 4'b1111;
                                
assign CS4 = CS_bus [3];
assign CS3 = CS_bus [2];
assign CS2 = CS_bus [1];
assign CS1 = CS_bus [0];

endmodule