cud.v

一个模拟ISA界面的简易小程式

// WARNING: Do NOT edit the input and output ports in this file in a text
// editor if you plan to continue editing the block that represents it in
// the Block Editor! File corruption is VERY likely to occur.

// Copyright (C) 1991-2009 Altera Corporation
// Your use of Altera Corporation's design tools, logic functions 
// and other software and tools, and its AMPP partner logic 
// functions, and any output files from any of the foregoing 
// (including device programming or simulation files), and any 
// associated documentation or information are expressly subject 
// to the terms and conditions of the Altera Program License 
// Subscription Agreement, Altera MegaCore Function License 
// Agreement, or other applicable license agreement, including, 
// without limitation, that your use is for the sole purpose of 
// programming logic devices manufactured by Altera and sold by 
// Altera or its authorized distributors.  Please refer to the 
// applicable agreement for further details.


// Generated by Quartus II Version 9.0 (Build Build 132 02/25/2009)
// Created on Thu Mar 19 21:45:05 2009

//  Module Declaration
module CUD
(
	// {{ALTERA_ARGS_BEGIN}} DO NOT REMOVE THIS LINE!
	clk, BALE, SA, IOW, IOR, SBHE, PC, PD, PA, PB, IOCS16, SD
	// {{ALTERA_ARGS_END}} DO NOT REMOVE THIS LINE!
);
// Port Declaration

	// {{ALTERA_IO_BEGIN}} DO NOT REMOVE THIS LINE!
	input clk;
	input BALE;
	input [15:0]SA;
	input IOW;
	input IOR;
	input SBHE;
	input [15:0]PC;
	input [15:0]PD;
	
	output [15:0]PA;
	output [15:0]PB;
	output IOCS16 = 1;
	inout [15:0]SD;
	reg [15:0]SDout,PA,PB;
	reg IOCS16;
	reg OE,holdIOR,holdIOW;
	// {{ALTERA_IO_END}} DO NOT REMOVE THIS LINE!
	
	assign SD = (OE)? SDout:16'bz;
	always@(posedge clk)
	begin
	
		//control IOCS#16 =1
		//if IOR ==1 && IOW ==1
		begin
			if(IOCS16 ==0)
			begin
				//hold IOR or IOW
				if(IOR==0)
					holdIOR = 1;
				else if(IOW ==0)
					holdIOW = 1;
				
				//Read Over or Write Over
				if(IOR & holdIOR || IOW & holdIOW)
					begin
					IOCS16 =1;
					holdIOR =0;
					holdIOW =0;
					end
			end
				
		end
		//check SA control IOCS#16
		//SA = 0x0300 OR 0x03100 IOCS#16 = 0 
		begin
			if (SA == 16'h0300 && BALE==1 && SBHE ==0)
				IOCS16 = 0;
			else if(SA == 16'h0310 && BALE==1 && SBHE ==0)
				IOCS16 = 0;
		end
		//IOR = 0 when OE = 1 begin READ
		begin
			if(IOR == 0)
				OE = 1;
			else if(IOR == 1)
				OE = 0;
		end
		
		//I/O read
		//IOR# = 0 0 AND SA = 0x0300 OR 0x0310
		//else SDout =0x0000
		begin
		if(IOR ==0 && SA == 16'h0300)
			SDout = PC;
		else if(IOR == 0 && SA == 16'h0310)
			SDout = PD;
		end
		
		//I/O write
		//IOW# = 0 AND SA = 0x0300 OR 0x0310
		begin
			if(IOW == 0 && SA == 16'h0300)
				PA <= SD;
			else if(IOW == 0 && SA == 16'h0310)
				PB <= SD;
		end
		
	end
	

endmodule