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/* $Id: aeMB2_xslif.v,v 1.7 2008-04-27 16:41:46 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/>.
*/
/**
 * Accelerator Interface
 * @file aeMB2_xslif.v
 
 * This sets up the Wishbone control signals for the XSL bus
   interface. This is a non optional bus interface. Bus transactions
   are independent of the pipeline.
 
 */
 
module aeMB2_xslif (/*AUTOARG*/
   // Outputs
   xwb_adr_o, xwb_dat_o, xwb_sel_o, xwb_tag_o, xwb_stb_o, xwb_cyc_o,
   xwb_wre_o, xwb_fb, xwb_mx,
   // Inputs
   xwb_dat_i, xwb_ack_i, imm_of, opc_of, opa_of, gclk, grst, dena,
   gpha
   );
   parameter AEMB_XSL = 1; ///< implement XSEL bus (ignored)
   parameter AEMB_XWB = 3; ///< XSEL bus width
 
   // XWB control signals   
   output [AEMB_XWB-1:2] xwb_adr_o;
   output [31:0] 	 xwb_dat_o;   
   output [3:0] 	 xwb_sel_o;
   output 		 xwb_tag_o;   
   output 		 xwb_stb_o,
			 xwb_cyc_o,
			 xwb_wre_o;
   input [31:0] 	 xwb_dat_i; 		 
   input 		 xwb_ack_i;   
 
   // INTERNAL
   output 		 xwb_fb;
   output [31:0] 	 xwb_mx;   
   input [15:0] 	 imm_of;
   input [5:0] 		 opc_of;    
   input [31:0] 	 opa_of;
 
   // SYS signals
   input 		 gclk,
			 grst,
			 dena,
			 gpha;   
 
   /*AUTOREG*/
   // Beginning of automatic regs (for this module's undeclared outputs)
   reg [AEMB_XWB-1:2]	xwb_adr_o;
   reg [31:0]		xwb_dat_o;
   reg [31:0]		xwb_mx;
   reg			xwb_stb_o;
   reg			xwb_tag_o;
   reg			xwb_wre_o;
   // End of automatics
 
   // FIXME: perform NGET/NPUT non-blocking operations
   assign 		xwb_fb = (xwb_stb_o ~^ xwb_ack_i);
 
   // XSEL bus
   reg [31:0] 		xwb_lat;
 
   always @(posedge gclk)
     if (grst) begin
	/*AUTORESET*/
	// Beginning of autoreset for uninitialized flops
	xwb_adr_o <= {(1+(AEMB_XWB-1)-(2)){1'b0}};
	xwb_dat_o <= 32'h0;
	xwb_mx <= 32'h0;
	xwb_tag_o <= 1'h0;
	xwb_wre_o <= 1'h0;
	// End of automatics
     end else if (dena) begin
 
	xwb_adr_o <= #1 imm_of[11:0]; // FSLx	
	xwb_wre_o <= #1 imm_of[15]; // PUT
	xwb_tag_o <= #1 imm_of[13]; // cGET/cPUT	
 
	xwb_dat_o <= #1 opa_of; // Latch output
 
	xwb_mx <= #1 (xwb_ack_i) ? 
		  xwb_dat_i : // stalled from XWB
		  xwb_lat; // Latch earlier
 
     end // if (dena)
 
   assign xwb_sel_o = 4'hF;   
 
   // Independent on pipeline
   reg 			xBLK;
 
   always @(posedge gclk)
     if (grst) begin
	/*AUTORESET*/
	// Beginning of autoreset for uninitialized flops
	xwb_lat <= 32'h0;
	// End of automatics
     end else if (xwb_ack_i) begin
	xwb_lat <= #1 xwb_dat_i;	
     end
 
   always @(posedge gclk)
     if (grst) begin
	/*AUTORESET*/
	// Beginning of autoreset for uninitialized flops
	xBLK <= 1'h0;
	xwb_stb_o <= 1'h0;
	// End of automatics
     end else if (xwb_fb) begin
	xBLK <= #1 imm_of[14]; // nGET/nPUT	
	xwb_stb_o <= #1 (dena) ? !opc_of[5] & opc_of[4] & opc_of[3] & opc_of[1] : // GET/PUT
		     (xwb_stb_o & !xwb_ack_i);	
     end
 
   assign xwb_cyc_o = xwb_stb_o;
   //assign xwb_stb_o = (AEMB_XSL[0]) ? xSTB : 1'bX;   
 
endmodule // aeMB2_xslif
 
/*
 $Log: not supported by cvs2svn $
 Revision 1.6  2008/04/27 16:04:12  sybreon
 Fixed minor typos.
 
 Revision 1.5  2008/04/26 17:57:43  sybreon
 Minor performance improvements.
 
 Revision 1.4  2008/04/26 01:09:06  sybreon
 Passes basic tests. Minor documentation changes to make it compatible with iverilog pre-processor.
 
 Revision 1.3  2008/04/21 12:11:38  sybreon
 Passes arithmetic tests with single thread.
 
 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.
*/