Witch of Git - nan-gate/blob - techlib.sv

   1 `define POS0 3'b000
   2 `define NEG0 3'b100
   3 `define POS1 3'b001
   4 `define NEG1 3'b101
   5 `define PINF 3'b010
   6 `define NINF 3'b110
   7 `define PNAN 3'b011
   8 `define NNAN 3'b111
   9 `define ANAN 3'b?11
  10 `define ANYF 3'b???
  11
  12 // A NaN gate! Computes `Inf - max(x+y, -Inf)`.
  13 // See http://tom7.org/nand/
  14 module nan(
  15     input      [2:0] A,
  16     input      [2:0] B, output reg [2:0] Y
  17 );
  18
  19 always begin
  20     casez ({A, B})
  21     {`ANYF, `ANAN}, {`ANAN, `ANYF}: Y = `PINF;
  22     {`PINF, `NINF}, {`NINF, `PINF}: Y = `PINF;
  23     {`ANYF, `PINF}, {`PINF, `ANYF}: Y = `PNAN;
  24     default: Y = `PINF;
  25     endcase
  26 end
  27 endmodule
  28
  29 // Convert a bit into an fp3
  30 module bit_to_fp3(input A, output [2:0] Y);
  31 assign Y = A ? `PNAN : `PINF;
  32 endmodule
  33
  34 // Convert an fp3 into a bit
  35 module fp3_to_bit(input [2:0] A, output reg Y);
  36 always begin
  37     case (A)
  38     `PNAN, `NNAN: Y = 1'b1;
  39     default: Y = 1'b0;
  40     endcase
  41 end
  42 endmodule
  43