//////////////////////////////////////////////////////////////////////
////                                                              ////
//// Copyright (C) 2014 leishangwen@163.com                       ////
////                                                              ////
//// 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.                                                     ////
////                                                              ////
//////////////////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////////////////
// Module:  ctrl
// File:    ctrl.v
// Author:  Lei Silei
// E-mail:  leishangwen@163.com
// Description: 控制模块，控制流水线的刷新、暂停等
// Revision: 1.0
//////////////////////////////////////////////////////////////////////

`include "defines.v"

module ctrl(

	input wire										rst,

	input wire[31:0]             excepttype_i,
	input wire[`RegBus]          cp0_epc_i,

	input wire                   stallreq_from_id,

  //来自执行阶段的暂停请求
	input wire                   stallreq_from_ex,

	output reg[`RegBus]          new_pc,
	output reg                   flush,	
	output reg[5:0]              stall       
	
);


	always @ (*) begin
		if(rst == `RstEnable) begin
			stall <= 6'b000000;
			flush <= 1'b0;
			new_pc <= `ZeroWord;
		end else if(excepttype_i != `ZeroWord) begin
		  flush <= 1'b1;
		  stall <= 6'b000000;
			case (excepttype_i)
				32'h00000001:		begin   //interrupt
					new_pc <= 32'h00000020;
				end
				32'h00000008:		begin   //syscall
					new_pc <= 32'h00000040;
				end
				32'h0000000a:		begin   //inst_invalid
					new_pc <= 32'h00000040;
				end
				32'h0000000d:		begin   //trap
					new_pc <= 32'h00000040;
				end
				32'h0000000c:		begin   //ov
					new_pc <= 32'h00000040;
				end
				32'h0000000e:		begin   //eret
					new_pc <= cp0_epc_i;
				end
				default	: begin
				end
			endcase 						
		end else if(stallreq_from_ex == `Stop) begin
			stall <= 6'b001111;
			flush <= 1'b0;		
		end else if(stallreq_from_id == `Stop) begin
			stall <= 6'b000111;	
			flush <= 1'b0;		
		end else begin
			stall <= 6'b000000;
			flush <= 1'b0;
			new_pc <= `ZeroWord;		
		end    //if
	end      //always
			

endmodule