驱动时钟加入了PLL,使得DDS的驱动时钟可变.32位的NCO使得DDS的分辨率可以做到Hz量级

				// megafunction wizard: %LPM_ADD_SUB%
				// GENERATION: STANDARD
				// VERSION: WM1.0
				// MODULE: lpm_add_sub 
				
				// ============================================================
				// File Name: add.v
				// Megafunction Name(s):
				// 			lpm_add_sub
				//
				// Simulation Library Files(s):
				// 			lpm
				// ============================================================
				// ************************************************************
				// THIS IS A WIZARD-GENERATED FILE. DO NOT EDIT THIS FILE!
				//
				// 7.2 Build 151 09/26/2007 SJ Full Version
				// ************************************************************
				
				
				//Copyright (C) 1991-2007 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.
				
				
				// synopsys translate_off
				`timescale 1 ps / 1 ps
				// synopsys translate_on
				module add (
					dataa,
					datab,
					result);
				
					input	[31:0]  dataa;
					input	[31:0]  datab;
					output	[31:0]  result;
				
					wire [31:0] sub_wire0;
					wire [31:0] result = sub_wire0[31:0];
				
					lpm_add_sub	lpm_add_sub_component (
								.dataa (dataa),
								.datab (datab),
								.result (sub_wire0)
								// synopsys translate_off
								,
								.aclr (),
								.add_sub (),
								.cin (),
								.clken (),
								.clock (),
								.cout (),
								.overflow ()
								// synopsys translate_on
								);
					defparam
						lpm_add_sub_component.lpm_direction = "ADD",
						lpm_add_sub_component.lpm_hint = "ONE_INPUT_IS_CONSTANT=NO,CIN_USED=NO",
						lpm_add_sub_component.lpm_type = "LPM_ADD_SUB",
						lpm_add_sub_component.lpm_width = 32;
				
				
				endmodule
				
				// ============================================================
				// CNX file retrieval info
				// ============================================================
				// Retrieval info: PRIVATE: CarryIn NUMERIC "0"
				// Retrieval info: PRIVATE: CarryOut NUMERIC "0"
				// Retrieval info: PRIVATE: ConstantA NUMERIC "0"
				// Retrieval info: PRIVATE: ConstantB NUMERIC "0"
				// Retrieval info: PRIVATE: Function NUMERIC "0"
				// Retrieval info: PRIVATE: INTENDED_DEVICE_FAMILY STRING "Cyclone II"
				// Retrieval info: PRIVATE: LPM_PIPELINE NUMERIC "0"
				// Retrieval info: PRIVATE: Latency NUMERIC "0"
				// Retrieval info: PRIVATE: Overflow NUMERIC "0"
				// Retrieval info: PRIVATE: RadixA NUMERIC "10"
				// Retrieval info: PRIVATE: RadixB NUMERIC "10"
				// Retrieval info: PRIVATE: SYNTH_WRAPPER_GEN_POSTFIX STRING "0"
				// Retrieval info: PRIVATE: ValidCtA NUMERIC "0"
				// Retrieval info: PRIVATE: ValidCtB NUMERIC "0"
				// Retrieval info: PRIVATE: WhichConstant NUMERIC "0"
				// Retrieval info: PRIVATE: aclr NUMERIC "0"
				// Retrieval info: PRIVATE: clken NUMERIC "0"
				// Retrieval info: PRIVATE: nBit NUMERIC "32"
				// Retrieval info: CONSTANT: LPM_DIRECTION STRING "ADD"
				// Retrieval info: CONSTANT: LPM_HINT STRING "ONE_INPUT_IS_CONSTANT=NO,CIN_USED=NO"
				// Retrieval info: CONSTANT: LPM_TYPE STRING "LPM_ADD_SUB"
				// Retrieval info: CONSTANT: LPM_WIDTH NUMERIC "32"
				// Retrieval info: USED_PORT: dataa 0 0 32 0 INPUT NODEFVAL dataa[31..0]
				// Retrieval info: USED_PORT: datab 0 0 32 0 INPUT NODEFVAL datab[31..0]
				// Retrieval info: USED_PORT: result 0 0 32 0 OUTPUT NODEFVAL result[31..0]
				// Retrieval info: CONNECT: result 0 0 32 0 @result 0 0 32 0
				// Retrieval info: CONNECT: @dataa 0 0 32 0 dataa 0 0 32 0
				// Retrieval info: CONNECT: @datab 0 0 32 0 datab 0 0 32 0
				// Retrieval info: LIBRARY: lpm lpm.lpm_components.all
				// Retrieval info: GEN_FILE: TYPE_NORMAL add.v TRUE
				// Retrieval info: GEN_FILE: TYPE_NORMAL add.inc FALSE
				// Retrieval info: GEN_FILE: TYPE_NORMAL add.cmp FALSE
				// Retrieval info: GEN_FILE: TYPE_NORMAL add.bsf TRUE FALSE
				// Retrieval info: GEN_FILE: TYPE_NORMAL add_inst.v FALSE
				// Retrieval info: GEN_FILE: TYPE_NORMAL add_bb.v TRUE
				// Retrieval info: GEN_FILE: TYPE_NORMAL add_waveforms.html TRUE
				// Retrieval info: GEN_FILE: TYPE_NORMAL add_wave*.jpg FALSE
				// Retrieval info: LIB_FILE: lpm