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// $Id: aeMB_ctrl.v,v 1.10 2007-11-30 16:44:40 sybreon Exp $

//

// AEMB CONTROL UNIT

// 

// Copyright (C) 2004-2007 Shawn Tan Ser Ngiap <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/>.

//

// $Log: not supported by cvs2svn $

// Revision 1.9  2007/11/15 09:26:43  sybreon

// Fixed minor typo causing synthesis failure.

//

// Revision 1.8  2007/11/14 23:19:24  sybreon

// Fixed minor typo.

//

// Revision 1.7  2007/11/14 22:14:34  sybreon

// Changed interrupt handling system (reported by M. Ettus).

//

// Revision 1.6  2007/11/10 16:39:38  sybreon

// Upgraded license to LGPLv3.

// Significant performance optimisations.

//

// Revision 1.5  2007/11/09 20:51:52  sybreon

// Added GET/PUT support through a FSL bus.

//

// Revision 1.4  2007/11/08 17:48:14  sybreon

// Fixed data WISHBONE arbitration problem (reported by J Lee).

//

// Revision 1.3  2007/11/08 14:17:47  sybreon

// Parameterised optional components.

//

// Revision 1.2  2007/11/02 19:20:58  sybreon

// Added better (beta) interrupt support.

// Changed MSR_IE to disabled at reset as per MB docs.

//

// Revision 1.1  2007/11/02 03:25:40  sybreon

// New EDK 3.2 compatible design with optional barrel-shifter and multiplier.

// Fixed various minor data hazard bugs.

// Code compatible with -O0/1/2/3/s generated code.

//

module aeMB_ctrl (/*AUTOARG*/

   // Outputs

   rMXDST, rMXSRC, rMXTGT, rMXALT, rMXALU, rRW, dwb_stb_o, dwb_wre_o,

   fsl_stb_o, fsl_wre_o,

   // Inputs

   rDLY, rIMM, rALT, rOPC, rRD, rRA, rRB, rPC, rBRA, rMSR_IE, xIREG,

   dwb_ack_i, iwb_ack_i, fsl_ack_i, gclk, grst, gena

   );

   // INTERNAL   

   //output [31:2] rPCLNK;

   output [1:0]  rMXDST;

   output [1:0]  rMXSRC, rMXTGT, rMXALT;

   output [2:0]  rMXALU;

   output [4:0]  rRW;

   input         rDLY;

   input [15:0]  rIMM;

   input [10:0]  rALT;

   input [5:0]    rOPC;

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

   input [31:2]  rPC;

   input         rBRA;

   input         rMSR_IE;

   input [31:0]  xIREG;

   // DATA WISHBONE

   output        dwb_stb_o;

   output        dwb_wre_o;

   input         dwb_ack_i;

   // INST WISHBONE

   input         iwb_ack_i;

   // FSL WISHBONE

   output        fsl_stb_o;

   output        fsl_wre_o;

   input         fsl_ack_i;

   // SYSTEM

   input         gclk, grst, gena;

   // --- DECODE INSTRUCTIONS

   // TODO: Simplify

   wire [5:0]     wOPC;

   wire [4:0]     wRD, wRA, wRB;

   wire [10:0]    wALT;

   assign        {wOPC, wRD, wRA, wRB, wALT} = xIREG; // FIXME: Endian

   wire          fSFT = (rOPC == 6'o44);

   wire          fLOG = ({rOPC[5:4],rOPC[2]} == 3'o4);

   wire          fMUL = (rOPC == 6'o20) | (rOPC == 6'o30);

   wire          fBSF = (rOPC == 6'o21) | (rOPC == 6'o31);

   wire          fDIV = (rOPC == 6'o22);

   wire          fRTD = (rOPC == 6'o55);

   wire          fBCC = (rOPC == 6'o47) | (rOPC == 6'o57);

   wire          fBRU = (rOPC == 6'o46) | (rOPC == 6'o56);

   wire          fBRA = fBRU & rRA[3];

   wire          fIMM = (rOPC == 6'o54);

   wire          fMOV = (rOPC == 6'o45);

   wire          fLOD = ({rOPC[5:4],rOPC[2]} == 3'o6);

   wire          fSTR = ({rOPC[5:4],rOPC[2]} == 3'o7);

   wire          fLDST = (&rOPC[5:4]);

   wire          fPUT = (rOPC == 6'o33) & rRB[4];

   wire          fGET = (rOPC == 6'o33) & !rRB[4];

   wire          wSFT = (wOPC == 6'o44);

   wire          wLOG = ({wOPC[5:4],wOPC[2]} == 3'o4);

   wire          wMUL = (wOPC == 6'o20) | (wOPC == 6'o30);

   wire          wBSF = (wOPC == 6'o21) | (wOPC == 6'o31);

   wire          wDIV = (wOPC == 6'o22);

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

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

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

   wire          wBRA = wBRU & wRA[3];

   wire          wIMM = (wOPC == 6'o54);

   wire          wMOV = (wOPC == 6'o45);

   wire          wLOD = ({wOPC[5:4],wOPC[2]} == 3'o6);

   wire          wSTR = ({wOPC[5:4],wOPC[2]} == 3'o7);

   wire          wLDST = (&wOPC[5:4]);

   wire          wPUT = (wOPC == 6'o33) & wRB[4];

   wire          wGET = (wOPC == 6'o33) & !wRB[4];

   // --- BRANCH SLOT REGISTERS ---------------------------

   reg [31:2]    rPCLNK, xPCLNK;

   reg [1:0]      rMXDST, xMXDST;

   reg [4:0]      rRW, xRW;

   reg [1:0]      rMXSRC, xMXSRC;

   reg [1:0]      rMXTGT, xMXTGT;

   reg [1:0]      rMXALT, xMXALT;

   // --- OPERAND SELECTOR ---------------------------------

   wire          wRDWE = |xRW;

   wire          wAFWD_M = (xRW == wRA) & (xMXDST == 2'o2) & wRDWE;

   wire          wBFWD_M = (xRW == wRB) & (xMXDST == 2'o2) & wRDWE;

   wire          wAFWD_R = (xRW == wRA) & (xMXDST == 2'o0) & wRDWE;

   wire          wBFWD_R = (xRW == wRB) & (xMXDST == 2'o0) & wRDWE;

   always @(/*AUTOSENSE*/rBRA or wAFWD_M or wAFWD_R or wBCC or wBFWD_M

            or wBFWD_R or wBRU or wOPC)

     //if (rBRA | |rXCE) begin

     if (rBRA) begin

        /*AUTORESET*/

        // Beginning of autoreset for uninitialized flops

        xMXALT <= 2'h0;

        xMXSRC <= 2'h0;

        xMXTGT <= 2'h0;

        // End of automatics

     end else begin

        xMXSRC <= (wBRU | wBCC) ? 2'o3 : // PC

                  (wAFWD_M) ? 2'o2 : // RAM

                  (wAFWD_R) ? 2'o1 : // FWD

                  2'o0; // REG

        xMXTGT <= (wOPC[3]) ? 2'o3 : // IMM

                  (wBFWD_M) ? 2'o2 : // RAM

                  (wBFWD_R) ? 2'o1 : // FWD

                  2'o0; // REG

        xMXALT <= (wAFWD_M) ? 2'o2 : // RAM

                  (wAFWD_R) ? 2'o1 : // FWD

                  2'o0; // REG  

     end // else: !if(rBRA)

   // --- ALU CONTROL ---------------------------------------

   reg [2:0]     rMXALU, xMXALU;

   always @(/*AUTOSENSE*/rBRA or wBRA or wBSF or wDIV or wLOG or wMOV

            or wMUL or wSFT)

     //if (rBRA | |rXCE) begin

     if (rBRA) begin

        /*AUTORESET*/

        // Beginning of autoreset for uninitialized flops

        xMXALU <= 3'h0;

        // End of automatics

     end else begin

        xMXALU <= (wBRA | wMOV) ? 3'o3 :

                  (wSFT) ? 3'o2 :

                  (wLOG) ? 3'o1 :

                  (wMUL) ? 3'o4 :

                  (wBSF) ? 3'o5 :

                  (wDIV) ? 3'o6 :

                  3'o0;

     end // else: !if(rBRA)

   // --- DELAY SLOT REGISTERS ------------------------------

   wire          fSKIP = (rBRA & !rDLY);

   always @(/*AUTOSENSE*/fBCC or fBRU or fGET or fLOD or fRTD or fSKIP

            or fSTR or rRD)

     if (fSKIP) begin

        /*AUTORESET*/

        // Beginning of autoreset for uninitialized flops

        xMXDST <= 2'h0;

        xRW <= 5'h0;

        // End of automatics

     end else begin

        xMXDST <= (fSTR | fRTD | fBCC) ? 2'o3 :

                  (fLOD | fGET) ? 2'o2 :

                  (fBRU) ? 2'o1 :

                  2'o0;

        xRW <= rRD;

     end // else: !if(fSKIP)

   // --- DATA WISHBONE ----------------------------------

   wire          fDACK = !(dwb_stb_o ^ dwb_ack_i);

   reg           rDWBSTB, xDWBSTB;

   reg           rDWBWRE, xDWBWRE;

   assign        dwb_stb_o = rDWBSTB;

   assign        dwb_wre_o = rDWBWRE;

   always @(/*AUTOSENSE*/fLOD or fSKIP or fSTR or iwb_ack_i)

     //if (fSKIP | |rXCE) begin

     if (fSKIP) begin

        /*AUTORESET*/

        // Beginning of autoreset for uninitialized flops

        xDWBSTB <= 1'h0;

        xDWBWRE <= 1'h0;

        // End of automatics

     end else begin

        xDWBSTB <= (fLOD | fSTR) & iwb_ack_i;

        xDWBWRE <= fSTR & iwb_ack_i;

     end

   always @(posedge gclk)

     if (grst) begin

        /*AUTORESET*/

        // Beginning of autoreset for uninitialized flops

        rDWBSTB <= 1'h0;

        rDWBWRE <= 1'h0;

        // End of automatics

     end else if (fDACK) begin

        rDWBSTB <= #1 xDWBSTB;

        rDWBWRE <= #1 xDWBWRE;

     end

   // --- FSL WISHBONE -----------------------------------

   wire          fFACK = !(fsl_stb_o ^ fsl_ack_i);

   reg           rFSLSTB, xFSLSTB;

   reg           rFSLWRE, xFSLWRE;

   assign        fsl_stb_o = rFSLSTB;

   assign        fsl_wre_o = rFSLWRE;

   always @(/*AUTOSENSE*/fGET or fPUT or fSKIP or iwb_ack_i)

     //if (fSKIP | |rXCE) begin

     if (fSKIP) begin

        /*AUTORESET*/

        // Beginning of autoreset for uninitialized flops

        xFSLSTB <= 1'h0;

        xFSLWRE <= 1'h0;

        // End of automatics

     end else begin

        xFSLSTB <= (fPUT | fGET) & iwb_ack_i;

        xFSLWRE <= fPUT & iwb_ack_i;

     end

   always @(posedge gclk)

     if (grst) begin

        /*AUTORESET*/

        // Beginning of autoreset for uninitialized flops

        rFSLSTB <= 1'h0;

        rFSLWRE <= 1'h0;

        // End of automatics

     end else if (fFACK) begin

        rFSLSTB <= #1 xFSLSTB;

        rFSLWRE <= #1 xFSLWRE;

     end

   // --- PIPELINE CONTROL DELAY ----------------------------

   always @(posedge gclk)

     if (grst) begin

        /*AUTORESET*/

        // Beginning of autoreset for uninitialized flops

        rMXALT <= 2'h0;

        rMXALU <= 3'h0;

        rMXDST <= 2'h0;

        rMXSRC <= 2'h0;

        rMXTGT <= 2'h0;

        rRW <= 5'h0;

        // End of automatics

     end else if (gena) begin // if (grst)

        //rPCLNK <= #1 xPCLNK;

        rMXDST <= #1 xMXDST;

        rRW <= #1 xRW;

        rMXSRC <= #1 xMXSRC;

        rMXTGT <= #1 xMXTGT;

        rMXALT <= #1 xMXALT;

        rMXALU <= #1 xMXALU;

     end

endmodule // aeMB_ctrl