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//////////////////////////////////////////////////////////////////////
////                                                              ////
////  OR1200's Exception logic                                    ////
////                                                              ////
////  This file is part of the OpenRISC 1200 project              ////
////  http://www.opencores.org/project,or1k                       ////
////                                                              ////
////  Description                                                 ////
////  Handles all OR1K exceptions inside CPU block.               ////
////                                                              ////
////  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                     ////
////                                                              ////
//////////////////////////////////////////////////////////////////////
//
// $Log: or1200_except.v,v $
//
// Revision 2.0  2010/06/30 11:00:00  ORSoC
// Major update: 
// Structure reordered and bugs fixed. 
 
// synopsys translate_off
`include "timescale.v"
// synopsys translate_on
`include "or1200_defines.v"
 
`define OR1200_EXCEPTFSM_WIDTH 3
`define OR1200_EXCEPTFSM_IDLE	`OR1200_EXCEPTFSM_WIDTH'd0
`define OR1200_EXCEPTFSM_FLU1 	`OR1200_EXCEPTFSM_WIDTH'd1
`define OR1200_EXCEPTFSM_FLU2 	`OR1200_EXCEPTFSM_WIDTH'd2
`define OR1200_EXCEPTFSM_FLU3 	`OR1200_EXCEPTFSM_WIDTH'd3
`define OR1200_EXCEPTFSM_FLU4 	`OR1200_EXCEPTFSM_WIDTH'd4
`define OR1200_EXCEPTFSM_FLU5 	`OR1200_EXCEPTFSM_WIDTH'd5
 
//
// Exception recognition and sequencing
//
 
module or1200_except
  (
   // Clock and reset
   clk, rst, 
 
   // Internal i/f
   sig_ibuserr, sig_dbuserr, sig_illegal, sig_align, sig_range, sig_dtlbmiss, 
   sig_dmmufault, sig_int, sig_syscall, sig_trap, sig_itlbmiss, sig_immufault, 
   sig_tick, ex_branch_taken, genpc_freeze, id_freeze, ex_freeze, wb_freeze,  
   if_stall,  if_pc, id_pc, ex_pc, wb_pc, id_flushpipe, ex_flushpipe, 
   extend_flush, except_flushpipe, except_type, except_start, except_started, 
   except_stop, except_trig, ex_void, abort_mvspr, branch_op, spr_dat_ppc, 
   spr_dat_npc, datain, du_dsr, epcr_we, eear_we, esr_we, pc_we, epcr, eear, 
   du_dmr1, du_hwbkpt, du_hwbkpt_ls_r, esr, sr_we, to_sr, sr, lsu_addr, 
   abort_ex, icpu_ack_i, icpu_err_i, dcpu_ack_i, dcpu_err_i, sig_fp, fpcsr_fpee
 
);
 
//
// I/O
//
input				clk;
input				rst;
input				sig_ibuserr;
input				sig_dbuserr;
input				sig_illegal;
input				sig_align;
input				sig_range;
input				sig_dtlbmiss;
input				sig_dmmufault;
input				sig_int;
input				sig_syscall;
input				sig_trap;
input				sig_itlbmiss;
input				sig_immufault;
input				sig_tick;
input   			sig_fp;
input    			fpcsr_fpee;   
input				ex_branch_taken;
input				genpc_freeze;
input				id_freeze;
input				ex_freeze;
input				wb_freeze;
input				if_stall;
input	[31:0]		if_pc;
output	[31:0]		id_pc;
output  [31:0]      ex_pc;
output  [31:0]      wb_pc;
input	[31:0]		datain;
input   [`OR1200_DU_DSR_WIDTH-1:0]     du_dsr;
input   [24:0]                       du_dmr1;
input			du_hwbkpt;
input			du_hwbkpt_ls_r;
input				epcr_we;
input				eear_we;
input				esr_we;
input				pc_we;
output	[31:0]			epcr;
output	[31:0]			eear;
output	[`OR1200_SR_WIDTH-1:0]	esr;
input	[`OR1200_SR_WIDTH-1:0]	to_sr;
input				sr_we;
input	[`OR1200_SR_WIDTH-1:0]	sr;
input	[31:0]			lsu_addr;
input              	id_flushpipe;
input              	ex_flushpipe;
output				except_flushpipe;
output				extend_flush;
output	[`OR1200_EXCEPT_WIDTH-1:0]	except_type;
output				except_start;
output				except_started;
output	[13:0]		except_stop;
output	[13:0]		except_trig;
input				ex_void;
input   [`OR1200_BRANCHOP_WIDTH-1:0]    branch_op; 
output	[31:0]			spr_dat_ppc;
output	[31:0]			spr_dat_npc;
output				abort_ex;
output              abort_mvspr;
input				icpu_ack_i;
input				icpu_err_i;
input				dcpu_ack_i;
input				dcpu_err_i;
 
//
// Internal regs and wires
//
reg	[`OR1200_EXCEPT_WIDTH-1:0]	except_type;
reg	[31:0]			id_pc;
reg                 id_pc_val;
reg	[31:0]			ex_pc;
reg                 ex_pc_val;
reg	[31:0]			wb_pc;
reg [31:0]          dl_pc;
reg	[31:0]			epcr;
reg	[31:0]			eear;
reg	[`OR1200_SR_WIDTH-1:0]		esr;
reg	[2:0]			id_exceptflags;
reg	[2:0]			ex_exceptflags;
reg	[`OR1200_EXCEPTFSM_WIDTH-1:0]	state;
reg				extend_flush;
reg				extend_flush_last;
reg				ex_dslot;
reg				delayed1_ex_dslot;
reg				delayed2_ex_dslot;
wire				except_started;
reg	[2:0]			delayed_iee;
reg	[2:0]			delayed_tee;
wire				int_pending;
wire				tick_pending;
wire    			fp_pending;
 
reg trace_trap      ;
reg ex_freeze_prev;
reg sr_ted_prev;
reg dsr_te_prev;
reg dmr1_st_prev    ;
reg dmr1_bt_prev    ;
wire dsr_te = ex_freeze_prev ? dsr_te_prev : du_dsr[`OR1200_DU_DSR_TE];
wire sr_ted = ex_freeze_prev ? sr_ted_prev : sr[`OR1200_SR_TED];
wire dmr1_st = ex_freeze_prev ? dmr1_st_prev: du_dmr1[`OR1200_DU_DMR1_ST] ;
wire dmr1_bt = ex_freeze_prev ? dmr1_bt_prev: du_dmr1[`OR1200_DU_DMR1_BT] ;
 
//
// Simple combinatorial logic
//
assign except_started = extend_flush & except_start;
 
assign except_start = (except_type != `OR1200_EXCEPT_NONE) & extend_flush;
 
assign int_pending = sig_int & (sr[`OR1200_SR_IEE] | 
				(sr_we & to_sr[`OR1200_SR_IEE])) 
		    & id_pc_val & delayed_iee[2] & ~ex_freeze & ~ex_branch_taken
		     & ~ex_dslot & ~(sr_we & ~to_sr[`OR1200_SR_IEE]);
 
assign tick_pending = sig_tick & (sr[`OR1200_SR_TEE] | 
				  (sr_we & to_sr[`OR1200_SR_TEE])) & id_pc_val
		      & delayed_tee[2] & ~ex_freeze & ~ex_branch_taken 
		      & ~ex_dslot & ~(sr_we & ~to_sr[`OR1200_SR_TEE]);
 
assign fp_pending = sig_fp & fpcsr_fpee & ~ex_freeze & ~ex_branch_taken 
		    & ~ex_dslot;
 
// Abort write into RF by load & other instructions   
assign abort_ex = sig_dbuserr | sig_dmmufault | sig_dtlbmiss | sig_align | 
		  sig_illegal | ((du_hwbkpt | trace_trap) & ex_pc_val 
				 & !sr_ted & !dsr_te);
 
// abort spr read/writes   
assign abort_mvspr  = sig_illegal | ((du_hwbkpt | trace_trap) & ex_pc_val 
				     & !sr_ted & !dsr_te) ; 
assign spr_dat_ppc = wb_pc;
 
assign spr_dat_npc = ex_void ? id_pc : ex_pc;
 
//
// Order defines exception detection priority
//
assign except_trig = {
		      ex_exceptflags[1]	& ~du_dsr[`OR1200_DU_DSR_IME],
		      ex_exceptflags[0]	& ~du_dsr[`OR1200_DU_DSR_IPFE],
		      ex_exceptflags[2]	& ~du_dsr[`OR1200_DU_DSR_BUSEE],
		      sig_illegal       & ~du_dsr[`OR1200_DU_DSR_IIE],
		      sig_align		& ~du_dsr[`OR1200_DU_DSR_AE],
		      sig_dtlbmiss	& ~du_dsr[`OR1200_DU_DSR_DME],
		      sig_trap		& ~du_dsr[`OR1200_DU_DSR_TE],
		      sig_syscall       & ~du_dsr[`OR1200_DU_DSR_SCE] & ~ex_freeze,
		      sig_dmmufault	& ~du_dsr[`OR1200_DU_DSR_DPFE],
		      sig_dbuserr	& ~du_dsr[`OR1200_DU_DSR_BUSEE],
		      sig_range		& ~du_dsr[`OR1200_DU_DSR_RE],
		      fp_pending	& ~du_dsr[`OR1200_DU_DSR_FPE],
		      int_pending 	& ~du_dsr[`OR1200_DU_DSR_IE],
		      tick_pending	& ~du_dsr[`OR1200_DU_DSR_TTE]
		      };
 
wire    trace_cond  = !ex_freeze && !ex_void && (1'b0
`ifdef OR1200_DU_DMR1_ST
    ||  dmr1_st
`endif
`ifdef OR1200_DU_DMR1_BT
    ||  ((branch_op != `OR1200_BRANCHOP_NOP) && (branch_op != `OR1200_BRANCHOP_RFE) && dmr1_bt)
`endif
    );
 
assign except_stop = {
			tick_pending		& du_dsr[`OR1200_DU_DSR_TTE],
			int_pending 		& du_dsr[`OR1200_DU_DSR_IE],
			ex_exceptflags[1]	& du_dsr[`OR1200_DU_DSR_IME],
			ex_exceptflags[0]	& du_dsr[`OR1200_DU_DSR_IPFE],
			ex_exceptflags[2]	& du_dsr[`OR1200_DU_DSR_BUSEE],
			sig_illegal		& du_dsr[`OR1200_DU_DSR_IIE],
			sig_align		& du_dsr[`OR1200_DU_DSR_AE],
			sig_dtlbmiss		& du_dsr[`OR1200_DU_DSR_DME],
			sig_dmmufault		& du_dsr[`OR1200_DU_DSR_DPFE],
			sig_dbuserr		& du_dsr[`OR1200_DU_DSR_BUSEE],
			sig_range		& du_dsr[`OR1200_DU_DSR_RE],
			sig_trap		& du_dsr[`OR1200_DU_DSR_TE],
		        fp_pending  		& du_dsr[`OR1200_DU_DSR_FPE],
			sig_syscall		& du_dsr[`OR1200_DU_DSR_SCE] & ~ex_freeze
		};
 
always @(posedge clk or posedge rst) begin
	if (rst) begin
		trace_trap  <=  1'b0 ;
	end 
	else if (!(trace_trap && !ex_pc_val)) begin
		trace_trap  <=  trace_cond & !dsr_te & !sr_ted ;
	end
end
 
always @(posedge clk or posedge rst) begin
	if (rst) begin
        ex_freeze_prev  <=  1'b0 ;
        sr_ted_prev     <=  1'b0 ;
        dsr_te_prev     <=  1'b0 ;
        dmr1_st_prev    <=  1'b0 ;
        dmr1_bt_prev    <=  1'b0 ;
    end 
    else begin
        ex_freeze_prev  <=  ex_freeze ;
        if (!ex_freeze_prev || ex_void) begin
            sr_ted_prev     <=  sr     [`OR1200_SR_TED    ] ;
            dsr_te_prev     <=  du_dsr [`OR1200_DU_DSR_TE ] ;
            dmr1_st_prev    <=  du_dmr1[`OR1200_DU_DMR1_ST] ;
            dmr1_bt_prev    <=  du_dmr1[`OR1200_DU_DMR1_BT] ;
        end
    end
end
 
//
// PC and Exception flags pipelines
//
always @(posedge clk or posedge rst) begin
	if (rst) begin
		id_pc <=  32'd0;
        id_pc_val <=  1'b0 ;
		id_exceptflags <=  3'b000;
	end
	else if (id_flushpipe) begin
        id_pc_val <=  1'b0 ;
		id_exceptflags <=  3'b000;
	end
	else if (!id_freeze) begin
		id_pc <=  if_pc;
        id_pc_val <=  1'b1 ;
		id_exceptflags <=  { sig_ibuserr, sig_itlbmiss, sig_immufault };
	end
end
 
//
// delayed_iee
//
// SR[IEE] should not enable interrupts right away
// when it is restored with l.rfe. Instead delayed_iee
// together with SR[IEE] enables interrupts once
// pipeline is again ready.
//
always @(posedge rst or posedge clk)
	if (rst)
		delayed_iee <=  3'b000;
	else if (!sr[`OR1200_SR_IEE])
		delayed_iee <=  3'b000;
	else
		delayed_iee <=  {delayed_iee[1:0], 1'b1};
 
//
// delayed_tee
//
// SR[TEE] should not enable tick exceptions right away
// when it is restored with l.rfe. Instead delayed_tee
// together with SR[TEE] enables tick exceptions once
// pipeline is again ready.
//
always @(posedge rst or posedge clk)
	if (rst)
		delayed_tee <=  3'b000;
	else if (!sr[`OR1200_SR_TEE])
		delayed_tee <=  3'b000;
	else
		delayed_tee <=  {delayed_tee[1:0], 1'b1};
 
//
// PC and Exception flags pipelines
//
always @(posedge clk or posedge rst) begin
	if (rst) begin
		ex_dslot <=  1'b0;
		ex_pc <=  32'd0;
                ex_pc_val <=  1'b0 ;
		ex_exceptflags <=  3'b000;
		delayed1_ex_dslot <=  1'b0;
		delayed2_ex_dslot <=  1'b0;
	end
	else if (ex_flushpipe) begin
		ex_dslot <=  1'b0;
                ex_pc_val <=  1'b0 ;
		ex_exceptflags <=  3'b000;
		delayed1_ex_dslot <=  1'b0;
		delayed2_ex_dslot <=  1'b0;
	end
	else if (!ex_freeze & id_freeze) begin
		ex_dslot <=  1'b0;
		ex_pc <=  id_pc;
                ex_pc_val <=  id_pc_val ;
		ex_exceptflags <=  3'b000;
		delayed1_ex_dslot <=  ex_dslot;
		delayed2_ex_dslot <=  delayed1_ex_dslot;
	end
	else if (!ex_freeze) begin
		ex_dslot <=  ex_branch_taken;
		ex_pc <=  id_pc;
                ex_pc_val <=  id_pc_val ;
		ex_exceptflags <=  id_exceptflags;
		delayed1_ex_dslot <=  ex_dslot;
		delayed2_ex_dslot <=  delayed1_ex_dslot;
	end
end
 
//
// PC and Exception flags pipelines
//
always @(posedge clk or posedge rst) begin
	if (rst) begin
		wb_pc <=  32'd0;
        dl_pc <=  32'd0;
	end
	else if (!wb_freeze) begin
		wb_pc <=  ex_pc;
        dl_pc <=  wb_pc;
	end
end
 
//
// We have started execution of exception handler:
//  1. Asserted for 3 clock cycles
//  2. Don't execute any instruction that is still in pipeline and is not part of exception handler
//
assign except_flushpipe = |except_trig & ~|state;
 
//
// Exception FSM that sequences execution of exception handler
//
// except_type signals which exception handler we start fetching in:
//  1. Asserted in next clock cycle after exception is recognized
//
   always @(posedge clk or posedge rst) begin
      if (rst) begin
	 state <=  `OR1200_EXCEPTFSM_IDLE;
	 except_type <=  `OR1200_EXCEPT_NONE;
	 extend_flush <=  1'b0;
	 epcr <=  32'b0;
	 eear <=  32'b0;
	 esr <=  {2'h1, {`OR1200_SR_WIDTH-3{1'b0}}, 1'b1};
	 extend_flush_last <=  1'b0;
      end
      else begin
`ifdef OR1200_CASE_DEFAULT
	 case (state)	// synopsys parallel_case
`else
	   case (state)	// synopsys full_case parallel_case
`endif
	     `OR1200_EXCEPTFSM_IDLE:
	       if (except_flushpipe) begin
		  state <=  `OR1200_EXCEPTFSM_FLU1;
		  extend_flush <=  1'b1;
		  esr <=  sr_we ? to_sr : sr;
		  casex (except_trig)
`ifdef OR1200_EXCEPT_ITLBMISS
		    14'b1x_xxxx_xxxx_xxxx: begin
		       except_type <=  `OR1200_EXCEPT_ITLBMISS;
		       eear <=  ex_dslot ? 
			       ex_pc : ex_pc;
		       epcr <=  ex_dslot ? 
			       wb_pc : ex_pc;
		    end
`endif
`ifdef OR1200_EXCEPT_IPF
		    14'b01_xxxx_xxxx_xxxx: begin
		       except_type <=  `OR1200_EXCEPT_IPF;
		       eear <=  ex_dslot ? 
			       ex_pc : delayed1_ex_dslot ? 
			       id_pc : delayed2_ex_dslot ? 
			       id_pc : id_pc;
		       epcr <=  ex_dslot ? 
			       wb_pc : delayed1_ex_dslot ? 
			       id_pc : delayed2_ex_dslot ? 
			       id_pc : id_pc;
		    end
`endif
`ifdef OR1200_EXCEPT_BUSERR
		    14'b00_1xxx_xxxx_xxxx: begin	// Insn. Bus Error
		       except_type <=  `OR1200_EXCEPT_BUSERR;
		       eear <=  ex_dslot ? 
			       wb_pc : ex_pc;
		       epcr <=  ex_dslot ? 
			       wb_pc : ex_pc;
		    end
`endif
`ifdef OR1200_EXCEPT_ILLEGAL
		    14'b00_01xx_xxxx_xxxx: begin
		       except_type <=  `OR1200_EXCEPT_ILLEGAL;
		       eear <=  ex_pc;
		       epcr <=  ex_dslot ? 
			       wb_pc : ex_pc;
		    end
`endif
`ifdef OR1200_EXCEPT_ALIGN
		    14'b00_001x_xxxx_xxxx: begin
		       except_type <=  `OR1200_EXCEPT_ALIGN;
		       eear <=  lsu_addr;
		       epcr <=  ex_dslot ? 
			       wb_pc : ex_pc;
		    end
`endif
`ifdef OR1200_EXCEPT_DTLBMISS
		    14'b00_0001_xxxx_xxxx: begin
		       except_type <=  `OR1200_EXCEPT_DTLBMISS;
		       eear <=  lsu_addr;
		       epcr <=  ex_dslot ? 
			       wb_pc : delayed1_ex_dslot ? 
			       dl_pc : ex_pc;
		    end
`endif
`ifdef OR1200_EXCEPT_TRAP			
		    14'b00_0000_1xxx_xxxx: begin
		       except_type <=  `OR1200_EXCEPT_TRAP;
		       epcr <=  ex_dslot ? 
			       wb_pc : delayed1_ex_dslot ? 
			       id_pc : ex_pc;
		    end
`endif
`ifdef OR1200_EXCEPT_SYSCALL
		    14'b00_0000_01xx_xxxx: begin
		       except_type <=  `OR1200_EXCEPT_SYSCALL;
		       epcr <=  ex_dslot ? 
			       wb_pc : delayed1_ex_dslot ? 
			       id_pc : delayed2_ex_dslot ? 
			       id_pc : id_pc;
		    end
`endif
`ifdef OR1200_EXCEPT_DPF
		    14'b00_0000_001x_xxxx: begin
		       except_type <=  `OR1200_EXCEPT_DPF;
		       eear <=  lsu_addr;
		       epcr <=  ex_dslot ? 
			       wb_pc : delayed1_ex_dslot ? 
			       dl_pc : ex_pc;
		    end
`endif
`ifdef OR1200_EXCEPT_BUSERR
		    14'b00_0000_0001_xxxx: begin	// Data Bus Error
		       except_type <=  `OR1200_EXCEPT_BUSERR;
		       eear <=  lsu_addr;
		       epcr <=  ex_dslot ? 
			       wb_pc : delayed1_ex_dslot ? 
			       dl_pc : ex_pc;
		    end
`endif
`ifdef OR1200_EXCEPT_RANGE
		    14'b00_0000_0000_1xxx: begin
		       except_type <=  `OR1200_EXCEPT_RANGE;
		       epcr <=  ex_dslot ? 
			       wb_pc : delayed1_ex_dslot ? 
			       id_pc : delayed2_ex_dslot ? 
			       id_pc : id_pc;
		    end
`endif
`ifdef OR1200_EXCEPT_FLOAT
		    14'b00_0000_0000_01xx: begin
		       except_type <=  `OR1200_EXCEPT_FLOAT;
		       epcr <=  id_pc;
		    end
`endif
`ifdef OR1200_EXCEPT_INT
		    14'b00_0000_0000_001x: begin
		       except_type <=  `OR1200_EXCEPT_INT;
		       epcr <=  id_pc;
		    end
`endif
`ifdef OR1200_EXCEPT_TICK
		    14'b00_0000_0000_0001: begin
		       except_type <=  `OR1200_EXCEPT_TICK;
		       epcr <=  id_pc;
		    end
`endif
		    default:
		      except_type <=  `OR1200_EXCEPT_NONE;
		  endcase
	       end
	       else if (pc_we) begin
		  state <=  `OR1200_EXCEPTFSM_FLU1;
		  extend_flush <=  1'b1;
	       end
	       else begin
		  if (epcr_we)
		    epcr <=  datain;
		  if (eear_we)
		    eear <=  datain;
		  if (esr_we)
		    esr <=  {datain[`OR1200_SR_WIDTH-1], 1'b1, datain[`OR1200_SR_WIDTH-3:0]};
	       end
	     `OR1200_EXCEPTFSM_FLU1:
	       if (icpu_ack_i | icpu_err_i | genpc_freeze)
		 state <=  `OR1200_EXCEPTFSM_FLU2;
	     `OR1200_EXCEPTFSM_FLU2:
`ifdef OR1200_EXCEPT_TRAP
	       if (except_type == `OR1200_EXCEPT_TRAP) begin
		  state <=  `OR1200_EXCEPTFSM_IDLE;
		  extend_flush <=  1'b0;
		  extend_flush_last <=  1'b0;
		  except_type <=  `OR1200_EXCEPT_NONE;
	       end
               else
`endif
		 state <=  `OR1200_EXCEPTFSM_FLU3;
	     `OR1200_EXCEPTFSM_FLU3:
	       begin
		  state <=  `OR1200_EXCEPTFSM_FLU4;
	       end
	     `OR1200_EXCEPTFSM_FLU4: begin
		state <=  `OR1200_EXCEPTFSM_FLU5;
		extend_flush <=  1'b0;
		extend_flush_last <=  1'b0; // damjan
	     end
`ifdef OR1200_CASE_DEFAULT
	     default: begin
`else
		`OR1200_EXCEPTFSM_FLU5: begin
`endif
		   if (!if_stall && !id_freeze) begin
		      state <=  `OR1200_EXCEPTFSM_IDLE;
		      except_type <=  `OR1200_EXCEPT_NONE;
		      extend_flush_last <=  1'b0;
		   end
		end
	   endcase
	 end
   end
 
endmodule