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//////////////////////////////////////////////////////////////////////
////                                                              ////
////  OR1200's Insn MMU top level                                 ////
////                                                              ////
////  This file is part of the OpenRISC 1200 project              ////
////  http://www.opencores.org/cores/or1k/                        ////
////                                                              ////
////  Description                                                 ////
////  Instantiation of all IMMU blocks.                           ////
////                                                              ////
////  To Do:                                                      ////
////   - make it smaller and faster                               ////
////                                                              ////
////  Author(s):                                                  ////
////      - Damjan Lampret, lampret@opencores.org                 ////
////                                                              ////
//////////////////////////////////////////////////////////////////////
////                                                              ////
//// Copyright (C) 2000 Authors and OPENCORES.ORG                 ////
////                                                              ////
//// This source file may be used and distributed without         ////
//// restriction provided that this copyright statement is not    ////
//// removed from the file and that any derivative work contains  ////
//// the original copyright notice and the associated disclaimer. ////
////                                                              ////
//// This source file 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 source 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 source; if not, download it   ////
//// from http://www.opencores.org/lgpl.shtml                     ////
////                                                              ////
//////////////////////////////////////////////////////////////////////
//
// CVS Revision History
//
// $Log: not supported by cvs2svn $
// Revision 1.1.1.1  2001/10/06 10:18:36  igorm
// no message
//
// Revision 1.1  2001/08/17 08:03:35  lampret
// *** empty log message ***
//
// Revision 1.2  2001/07/22 03:31:53  lampret
// Fixed RAM's oen bug. Cache bypass under development.
//
// Revision 1.1  2001/07/20 00:46:03  lampret
// Development version of RTL. Libraries are missing.
//
//
 
// synopsys translate_off
`include "timescale.v"
// synopsys translate_on
`include "defines.v"
 
//
// Insn MMU
//
 
module immu(
	// Rst and clk
	clk, rst,
 
	// Fetch i/f
	immu_en, supv, immufetch_vaddr, immufetch_op, immufetch_stall,
 
	// Except I/F
	immuexcept_miss, immuexcept_fault,
 
	// SPR access
	spr_cs, spr_write, spr_addr, spr_dat_i, spr_dat_o,
 
	// IC i/f
	icimmu_paddr
);
 
parameter dw = `OPERAND_WIDTH;
parameter aw = `OPERAND_WIDTH;
 
//
// I/O
//
 
//
// Clock and reset
//
input				clk;
input				rst;
 
//
// FETCH I/F
//
input				immu_en;
input				supv;
input	[aw-1:0]		immufetch_vaddr;
input				immufetch_op;
output				immufetch_stall;
 
//
// Exception I/F
//
output				immuexcept_miss;
output				immuexcept_fault;
 
//
// SPR access
//
input				spr_cs;
input				spr_write;
input	[aw-1:0]		spr_addr;
input	[31:0]			spr_dat_i;
output	[31:0]			spr_dat_o;
 
//
// IC I/F
//
output	[aw-1:0]		icimmu_paddr;
 
//
// Internal wires and regs
//
wire				itlb_spr_access;
wire	[31:13]			itlb_ppn;
wire				itlb_hit;
wire				itlb_uxe;
wire				itlb_sxe;
wire	[31:0]			itlb_dat_o;
 
//
// Implemented bits inside match and translate registers
//
// itlbwYmrX: vpn 31-10  v 0
// itlbwYtrX: ppn 31-10  uxe 7  sxe 6
//
// itlb memory width:
// 19 bits for ppn
// 13 bits for vpn
// 1 bit for valid
// 2 bits for protection
 
`ifdef OR1200_NO_IMMU
 
//
// Put all outputs in inactive state
//
assign immufetch_stall = 1'b0;
assign immuexcept_miss = 1'b0;
assign immuexcept_fault = 1'b0;
assign spr_dat_o = 32'h00000000;
assign icimmu_paddr = immufetch_vaddr;
 
`else
 
//
// ITLB SPR access
//
// 1400 - 1600  itlbmr w0-3
// 1400 - 1480  itlbmr w0
// 1400 - 1440  itlbmr w0 [63:0]
//
// 1600 - 1800  itlbtr w0-3
// 1600 - 1680  itlbtr w0
// 1600 - 1640  itlbtr w0 [63:0]
//
assign itlb_spr_access = spr_cs & spr_addr[10];
 
//
// Physical address is either translated virtual address or
// simply equal when IMMU is disabled
//
assign icimmu_paddr = immu_en ? {itlb_ppn, immufetch_vaddr[12:0]} : immufetch_vaddr;
 
//
// Output to SPRS unit
//
assign spr_dat_o = itlb_spr_access ? itlb_dat_o : 32'h00000000;
 
//
// IMMU stall
//
assign immufetch_stall = 1'b0;
 
//
// Page fault exception logic
//
assign immuexcept_fault = immu_en &&
			(  (immufetch_op & !supv & !itlb_uxe) // Fetch in user mode not enabled
			|| (immufetch_op & supv & !itlb_sxe) ); // Fetch in supv mode not enabled
 
//
// TLB Miss exception logic
//
assign immuexcept_miss = immufetch_op && immu_en && !itlb_hit;
 
//
// Instantiation of ITLB
//
itlb itlb(
	// Rst and clk
        .clk(clk),
	.rst(rst),
 
        // I/F for translation
        .tlb_en(immu_en),
	.vaddr(immufetch_vaddr),
	.hit(itlb_hit),
	.ppn(itlb_ppn),
	.uxe(itlb_uxe),
	.sxe(itlb_sxe),
 
        // SPR access
        .spr_cs(itlb_spr_access),
	.spr_write(spr_write),
	.spr_addr(spr_addr),
	.spr_dat_i(spr_dat_i),
	.spr_dat_o(itlb_dat_o)
);
 
`endif
 
endmodule