Bit slicing in verilog

Question

How can I write wdata[((8*j)+7) : (8*i)] = $random; in verilog programming language? , where i and j are reg type variable. Modelsim gives error for constant range variable. How could I write it in proper manner.

Answer 1

You should think from Hardware prospective for the solution.

Here is one solution. Hope that it will help you.

module temp(clk);
  input clk;
  reg i, j;
  reg [23:0] register, select;
  wire [23:0] temp;

  initial 
  begin
      i = 'd1;
      j = 'd1;
  end

  generate
  for(genvar i = 0; i<24; i++)
  begin
      assign temp[i] = select[i] ? $random : register[i]; 
  end
  endgenerate

  always @ (posedge clk)
  begin
      register <= temp;
  end

  always @ *
  begin
      select = (32'hffff_ffff << ((j<<3)+8)) ^ (32'hffff_ffff << (i<<3));
  end
endmodule