Subversion Repositories zet86

/*

 *  Copyright (c) 2008  Zeus Gomez Marmolejo <zeus@opencores.org>

 *

 *  This file is part of the Zet processor. This processor is free

 *  hardware; you can redistribute it and/or modify it under the terms of

 *  the GNU General Public License as published by the Free Software

 *  Foundation; either version 3, or (at your option) any later version.

 *

 *  Zet is distrubuted in the hope that it will be useful, but WITHOUT

 *  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY

 *  or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public

 *  License for more details.

 *

 *  You should have received a copy of the GNU General Public License

 *  along with Zet; see the file COPYING. If not, see

 *  <http://www.gnu.org/licenses/>.

 */

`timescale 1ns/10ps

module jmp_cond (

    input [4:0]  logic_flags,

    input [3:0]  cond,

    input        is_cx,

    input [15:0] cx,

    output reg   jmp

  );

  // Net declarations

  wire of, sf, zf, pf, cf;

  wire cx_zero;

  // Assignments

  assign of = logic_flags[4];

  assign sf = logic_flags[3];

  assign zf = logic_flags[2];

  assign pf = logic_flags[1];

  assign cf = logic_flags[0];

  assign cx_zero = ~(|cx);

  // Behaviour

  always @(cond or is_cx or cx_zero or zf or of or cf or sf or pf)

    if (is_cx) case (cond)

        4'b0000: jmp <= cx_zero;         /* jcxz   */

        4'b0001: jmp <= ~cx_zero;        /* loop   */

        4'b0010: jmp <= zf & ~cx_zero;   /* loopz  */

        default: jmp <= ~zf & ~cx_zero; /* loopnz */

      endcase

    else case (cond)

      4'b0000: jmp <= of;

      4'b0001: jmp <= ~of;

      4'b0010: jmp <= cf;

      4'b0011: jmp <= ~cf;

      4'b0100: jmp <= zf;

      4'b0101: jmp <= ~zf;

      4'b0110: jmp <= cf | zf;

      4'b0111: jmp <= ~cf & ~zf;

      4'b1000: jmp <= sf;

      4'b1001: jmp <= ~sf;

      4'b1010: jmp <= pf;

      4'b1011: jmp <= ~pf;

      4'b1100: jmp <= (sf ^ of);

      4'b1101: jmp <= (sf ^~ of);

      4'b1110: jmp <= zf | (sf ^ of);

      4'b1111: jmp <= ~zf & (sf ^~ of);

    endcase

endmodule