Merge nyus:/storage/git/firearm

[firearm.git] / Execute.v

diff --git a/Execute.v b/Execute.v
index 5ba0a9a96aea7101a701cc0496893581f9c8e4a1..d7b4ba6485036b666a5cee9b6c6d0309870c035f 100644 (file)
--- a/Execute.v
+++ b/Execute.v
@@ -15,7 +15,56 @@ module Execute(
        input carry,
        
        output reg outstall = 0,
-       output reg outbubble = 1
+       output reg outbubble = 1,
+       output reg write_reg = 1'bx,
+       output reg [3:0] write_num = 4'bxxxx,
+       output reg [31:0] write_data = 32'hxxxxxxxx
        );
        
+       reg mult_start;
+       reg [31:0] mult_acc0, mult_in0, mult_in1;
+       wire mult_done;
+       wire [31:0] mult_result;
+       
+       Multiplier multiplier(
+               .clk(clk), .Nrst(Nrst),
+               .start(mult_start), .acc0(mult_acc0), .in0(mult_in0),
+               .in1(mult_in1), .done(mult_done), .result(mult_result));
+endmodule
+
+module Multiplier(
+       input clk,
+       input Nrst,     /* XXX not used yet */
+       
+       input start,
+       input [31:0] acc0,
+       input [31:0] in0,
+       input [31:0] in1,
+       
+       output reg done = 0,
+       output reg [31:0] result);
+       
+       reg [31:0] bitfield;
+       reg [31:0] multiplicand;
+       reg [31:0] acc;
+       
+       always @(posedge clk)
+       begin
+               if (start) begin
+                       bitfield <= in0;
+                       multiplicand <= in1;
+                       acc <= acc0;
+                       done <= 0;
+               end else begin
+                       bitfield <= {2'b00, bitfield[31:2]};
+                       multiplicand <= {multiplicand[29:0], 2'b00};
+                       acc <= acc +
+                               (bitfield[0] ? multiplicand : 0) +
+                               (bitfield[1] ? {multiplicand[30:0], 1'b0} : 0);
+                       if (bitfield == 0) begin
+                               result <= acc;
+                               done <= 1;
+                       end
+               end
+       end
 endmodule