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// $Id: aeMB_regf.v,v 1.1 2007-11-02 03:25:41 sybreon Exp $

//

// AEMB REGISTER FILE

// 

// Copyright (C) 2004-2007 Shawn Tan Ser Ngiap <shawn.tan@aeste.net>

//  

// This library 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 2.1 of

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

//

// This library 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 this library; if not, write to the Free Software

// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307

// USA

//

// $Log: not supported by cvs2svn $

module aeMB_regf (/*AUTOARG*/

   // Outputs

   rREGA, rREGB, rDWBDI, dwb_dat_o,

   // Inputs

   rOPC, rRA, rRB, rRW, rRD, rMXDST, rPCLNK, rRESULT, rDWBSEL, rBRA,

   rDLY, dwb_dat_i, gclk, grst, gena

   );

   // INTERNAL

   output [31:0] rREGA, rREGB;

   output [31:0] rDWBDI;

   input [5:0]    rOPC;

   input [4:0]    rRA, rRB, rRW, rRD;

   input [1:0]    rMXDST;

   input [31:2]  rPCLNK;

   input [31:0]  rRESULT;

   input [3:0]    rDWBSEL;

   input         rBRA, rDLY;

   // DATA WISHBONE

   output [31:0] dwb_dat_o;

   input [31:0]  dwb_dat_i;

   // SYSTEM

   input         gclk, grst, gena;

   // --- LOAD SIZER ----------------------------------------------

   // Moves the data bytes around depending on the size of the

   // operation.

   wire [31:0]    wDWBDI = dwb_dat_i; // FIXME: Endian   

   reg [31:0]     rDWBDI;

   always @(/*AUTOSENSE*/rDWBSEL or wDWBDI)

     case (rDWBSEL)

       // 8'bit

       4'h8: rDWBDI <= {24'd0, wDWBDI[31:24]};

       4'h4: rDWBDI <= {24'd0, wDWBDI[23:16]};

       4'h2: rDWBDI <= {24'd0, wDWBDI[15:8]};

       4'h1: rDWBDI <= {24'd0, wDWBDI[7:0]};

       // 16'bit

       4'hC: rDWBDI <= {16'd0, wDWBDI[31:16]};

       4'h3: rDWBDI <= {16'd0, wDWBDI[15:0]};

       // 32'bit

       4'hF: rDWBDI <= wDWBDI;

       // Undefined

       default: rDWBDI <= 32'hX;

     endcase

   // --- GENERAL PURPOSE REGISTERS (R0-R31) -----------------------

   // LUT RAM implementation is smaller and faster. R0 gets written

   // during reset with 0x00 and doesn't change after.

   reg [31:0]     mARAM[0:31],

                 mBRAM[0:31],

                 mDRAM[0:31];

   wire [31:0]    rREGW = mDRAM[rRW];

   wire [31:0]    rREGD = mDRAM[rRD];

   assign        rREGA = mARAM[rRA];

   assign        rREGB = mBRAM[rRB];

   wire          fRDWE = |rRW;

   reg [31:0]     xWDAT;

   always @(/*AUTOSENSE*/rDWBDI or rMXDST or rPCLNK or rREGW

            or rRESULT)

     case (rMXDST)

       2'o2: xWDAT <= rDWBDI;

       2'o1: xWDAT <= {rPCLNK, 2'o0};

       2'o0: xWDAT <= rRESULT;

       2'o3: xWDAT <= rREGW; // No change       

     endcase // case (rMXDST)

   always @(posedge gclk)

     if (grst | fRDWE) begin

        mARAM[rRW] <= xWDAT;

        mBRAM[rRW] <= xWDAT;

        mDRAM[rRW] <= xWDAT;

     end

   // --- STORE SIZER ---------------------------------------------

   // Replicates the data bytes across depending on the size of the

   // operation.

   wire [31:0]    xDST;

   wire          fDFWD_M = (rRW == rRD) & (rMXDST == 2'o2) & fRDWE;

   wire          fDFWD_R = (rRW == rRD) & (rMXDST == 2'o0) & fRDWE;

   reg [31:0]     rDWBDO, xDWBDO;

   assign        dwb_dat_o = rDWBDO;

   assign        xDST = (fDFWD_M) ? rDWBDI :

                        (fDFWD_R) ? rRESULT :

                        rREGD;

   always @(/*AUTOSENSE*/rOPC or xDST)

     case (rOPC[1:0])

       // 8'bit

       2'h0: xDWBDO <= {(4){xDST[7:0]}};

       // 16'bit

       2'h1: xDWBDO <= {(2){xDST[15:0]}};

       // 32'bit

       2'h2: xDWBDO <= xDST;

       default: xDWBDO <= 32'hX;

     endcase // case (rOPC[1:0])   

   always @(posedge gclk)

     if (grst) begin

        /*AUTORESET*/

        // Beginning of autoreset for uninitialized flops

        rDWBDO <= 32'h0;

        // End of automatics

     end else if (gena) begin

        rDWBDO <= #1 xDWBDO;

     end

   // --- SIMULATION ONLY ------------------------------------------

   // Randomise memory to simulate real-world memory

   // synopsys translate_off

   integer i;

   initial begin

      for (i=0; i<32; i=i+1) begin

         mARAM[i] <= $random;

         mBRAM[i] <= $random;

         mDRAM[i] <= $random;

      end

   end

   // synopsys translate_on

endmodule // aeMB_regf