Subversion Repositories fluid_core_2

//////////////////////////////////////////////////////////////////////
////                                                              ////
//// Copyright (C) 2014-2015 Azmath Moosa                         ////
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//// 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  ////
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//// This source file is free software; you can redistribute it   ////
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//// useful, but WITHOUT ANY WARRANTY; without even the implied   ////
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//// PURPOSE.  See the GNU Lesser General Public License for more ////
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//// from http://www.opencores.org/lgpl.shtml                     ////
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//////////////////////////////////////////////////////////////////////
`timescale 1ns / 1ps
`include "Configuration.v"
 
module IF_Stage(
	input Clk,
	input RST,
	input stall,
	input intr,
	input return_back,
	input [0:`pc_w] intr_vector,
	input [0:`inst_w] exInstruction,
	input [0:`pc_w] branch_target,
	input branch, linked,
	inout [0:3] stkFlag,
	output [0:`pc_w] exInstAddr,
	output exInstClk,
	output [0:`IF_ID_reg_w] IF_ID_reg
    );
 
 
	reg [0:`pc_w] PC;
	reg [0:`inst_w] IR;
	reg [0:`pc_w+4] PCStack [0:3];
	reg [0:1] PCStackPtr;
	reg HLT;
 
initial begin
PC <= 0;
IR <=0;
PCStackPtr <= 0;
end
 
always@ (posedge Clk) begin
	if (RST) begin
		PC <=0;
		IR <= 0;
		PCStackPtr <= 0;
		HLT <= 0;
	end else if (~HLT) begin
 
		if (intr) begin
		PCStack[PCStackPtr] <= {PC,stkFlag};
		PCStackPtr <= PCStackPtr + 1;
		PC <= intr_vector;
		end else if (branch) begin
			if (linked) begin
			PCStack[PCStackPtr] <= {PC+1,stkFlag};
			PCStackPtr <= PCStackPtr + 1;
			end
		PC <= branch_target;
		end else if (return_back) begin
		PCStackPtr <= PCStackPtr - 1;
		PC <= PCStack[PCStackPtr-1][0:`pc_w];
		end else if (~stall) begin
		PC <= PC + 1;
		IR <= exInstruction;
		HLT <= &exInstruction[0:`uop_vector_msb];
		end
 
	end
end
 
assign stkFlag = return_back ? PCStack[PCStackPtr][`pc_w+1:`pc_w+4]:'bz;
 
assign exInstAddr = PC;
assign exInstClk = Clk;
 
assign IF_ID_reg = IR;
 
endmodule