Fetch.v

   1 module Fetch(
   2         input clk,
   3         input Nrst,
   4
   5         output wire [31:0] rd_addr,
   6         output wire rd_req,
   7         input rd_wait,
   8         input [31:0] rd_data,
   9
  10         input stall,
  11         input jmp,
  12         input [31:0] jmppc,
  13         output reg bubble = 1,
  14         output reg [31:0] insn = 0,
  15         output reg [31:0] pc = 32'hFFFFFFFC);
  16
  17         reg qjmp = 0;   /* A jump has been queued up while we were waiting. */
  18         reg [31:0] qjmppc;
  19         always @(posedge clk)
  20                 if ((rd_wait || stall) && jmp && !qjmp)
  21                         {qjmp,qjmppc} <= {jmp, jmppc};
  22                 else if (!rd_wait && !stall && qjmp)    /* It has already been intoed. */
  23                         {qjmp,qjmppc} <= {1'b0, 32'hxxxxxxxx};
  24
  25         reg [31:0] reqpc;
  26         always @(*)
  27                 if (stall)
  28                         reqpc = pc;
  29                 else if (qjmp)
  30                         reqpc = qjmppc;
  31                 else if (jmp)
  32                         reqpc = jmppc;
  33                 else
  34                         reqpc = pc + 4;
  35
  36         assign rd_addr = reqpc;
  37         assign rd_req = 1;
  38
  39         always @(negedge Nrst)
  40         begin
  41                 pc <= 32'hFFFFFFFC;
  42                 qjmp <= 0;
  43                 bubble <= 1;
  44         end
  45
  46         always @(posedge clk)
  47         begin
  48                 if (!Nrst) begin
  49                         pc <= 32'hFFFFFFFC;
  50                         qjmp <= 0;
  51                         bubble <= 1;
  52                 end else if (!stall)
  53                 begin
  54                         bubble <= rd_wait;
  55                         insn <= rd_data;
  56                         if (!rd_wait)
  57                                 pc <= reqpc;
  58                 end
  59         end
  60 endmodule