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/* $Id: aeMB2_brcc.v,v 1.3 2008-04-26 01:09:05 sybreon Exp $

**

** AEMB2 EDK 6.2 COMPATIBLE CORE

** Copyright (C) 2004-2008 Shawn Tan <shawn.tan@aeste.net>

**

** This file is part of AEMB.

**

** AEMB is free software: you can redistribute it and/or modify it

** under the terms of the GNU Lesser General Public License as

** published by the Free Software Foundation, either version 3 of the

** License, or (at your option) any later version.

**

** AEMB is distributed 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 Lesser General

** Public License for more details.

**

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

** License along with AEMB. If not, see <http:**www.gnu.org/licenses/>.

*/

/**

 * Branch Condition Checker

 * @file aeMB2_brcc.v

 * This controls the decision to branch/delay. The actualy branch

   target is calculated in the ALU.

 */

module aeMB2_brcc (/*AUTOARG*/

   // Outputs

   bra_ex,

   // Inputs

   opd_of, ra_of, rd_of, opc_of, gclk, grst, dena, iena, gpha

   );

   parameter AEMB_HTX = 1;

   input [31:0] opd_of;

   input [4:0]   ra_of;

   input [4:0]   rd_of;

   input [5:0]   opc_of;

   output [1:0] bra_ex;

   // SYS signals

   input        gclk,

                grst,

                dena,

                iena,

                gpha;

   /*AUTOREG*/

   // Beginning of automatic regs (for this module's undeclared outputs)

   reg [1:0]             bra_ex;

   // End of automatics

   // TODO: replace comparators with logic

   /* Branch Control */

   wire         wRTD = (opc_of == 6'o55);

   wire         wBCC = (opc_of == 6'o47) | (opc_of == 6'o57);

   wire         wBRU = (opc_of == 6'o46) | (opc_of == 6'o56);

   wire         wBEQ = (opd_of == 32'd0);

   wire         wBLT = opd_of[31];

   wire         wBLE = wBLT | wBEQ;

   wire         wBNE = ~wBEQ;

   wire         wBGE = ~wBLT;

   wire         wBGT = ~wBLE;

   reg           xcc;

   always @(/*AUTOSENSE*/rd_of or wBEQ or wBGE or wBGT or wBLE or wBLT

            or wBNE) begin

      case (rd_of[2:0])

        3'o0: xcc <= wBEQ;

        3'o1: xcc <= wBNE;

        3'o2: xcc <= wBLT;

        3'o3: xcc <= wBLE;

        3'o4: xcc <= wBGT;

        3'o5: xcc <= wBGE;

        default: xcc <= 1'bX;

      endcase // case (rd_of[2:0])

   end // always @ (...

   always @(posedge gclk)

     if (grst) begin

        /*AUTORESET*/

        // Beginning of autoreset for uninitialized flops

        bra_ex <= 2'h0;

        // End of automatics

     end else if (dena) begin

        bra_ex[1] <= #1 (wRTD | wBRU | (wBCC & xcc)); // branch

        bra_ex[0] <= #1 (wBRU) ? ra_of[4] : rd_of[4]; // delay   

     end

endmodule // aeMB2_brcc

/*

 $Log: not supported by cvs2svn $

 Revision 1.2  2008/04/20 16:34:32  sybreon

 Basic version with some features left out.

 Revision 1.1  2008/04/18 00:21:52  sybreon

 Initial import.

*/