1、IBUFGDS輸入全局時鐘及DCM分頻使用：

IBUFGDS #(

.DIFF_TERM(FALSE), // DifferenTIal TerminaTIon (Virtex-4/5, Spartan-3E/3A)

.IOSTANDARD(DEFAULT) // Specifies the I/O standard for this buffer

) IBUFGDS_inst (

.O(CLK_SYS), // Clock buffer output

.I(CLKP_SYS), // Diff_p clock buffer input

.IB(CLKN_SYS) // Diff_n clock buffer input

);

DCM_BASE #(

.CLKDV_DIVIDE(2.0), // Divide by: 1.5,2.0,2.5,3.0,3.5,4.0,4.5,5.0,5.5,6.0,6.5

// 7.0,7.5,8.0,9.0,10.0,11.0,12.0,13.0,14.0,15.0 or 16.0

.CLKFX_DIVIDE(3), // Can be any integer from 1 to 32

.CLKFX_MULTIPLY(2), // Can be any integer from 2 to 32

.CLKIN_DIVIDE_BY_2(FALSE), // TRUE/FALSE to enable CLKIN divide by two feature

.CLKIN_PERIOD(8.14),//(10.0), // Specify period of input clock in ns from 1.25 to 1000.00

.CLKOUT_PHASE_SHIFT(NONE), // Specify phase shift mode of NONE or FIXED

.CLK_FEEDBACK(1X), // Specify clock feedback of NONE, 1X or 2X

.DCM_PERFORMANCE_MODE(MAX_SPEED), // Can be MAX_SPEED or MAX_RANGE

.DESKEW_ADJUST(SYSTEM_SYNCHRONOUS), // SOURCE_SYNCHRONOUS, SYSTEM_SYNCHRONOUS or

// an integer from 0 to 15

.DFS_FREQUENCY_MODE(LOW), // LOW or HIGH frequency mode for frequency synthesis

.DLL_FREQUENCY_MODE(LOW), // LOW, HIGH, or HIGH_SER frequency mode for DLL

.DUTY_CYCLE_CORRECTION(TRUE), // Duty cycle correction, TRUE or FALSE

.FACTORY_JF(16'hf0f0), // FACTORY JF value suggested to be set to 16'hf0f0

.PHASE_SHIFT(0), // Amount of fixed phase shift from -255 to 1023

.STARTUP_WAIT(FALSE) // Delay configuration DONE until DCM LOCK, TRUE/FALSE

) DCM_BASE_inst (

.CLK0(CLK0), // 0 degree DCM CLK output

.CLK180(CLK180), // 180 degree DCM CLK output

.CLK270(CLK270), // 270 degree DCM CLK output

.CLK2X(CLK2X), // 2X DCM CLK output

.CLK2X180(CLK2X180), // 2X, 180 degree DCM CLK out

.CLK90(CLK90), // 90 degree DCM CLK output

.CLKDV(clk4608), // Divided DCM CLK out (CLKDV_DIVIDE)

.CLKFX(clk), // DCM CLK synthesis out (M/D)

.CLKFX180(CLKFX180), // 180 degree CLK synthesis out

.LOCKED(LOCKED), // DCM LOCK status output

.CLKFB(CLK0), // DCM clock feedback

.CLKIN(CLK_SYS), // Clock input (from IBUFG, BUFG or DCM)

.RST(1'b0) // DCM asynchronous reset input

);

2、ODDR、IDDR單邊緣與雙邊緣觸發(fā)的轉(zhuǎn)換。

單邊緣輸入雙邊緣輸出：

ODDR #(

.DDR_CLK_EDGE(OPPOSITE_EDGE), // OPPOSITE_EDGE or SAME_EDGE

.INIT(1'b0), // Initial value of Q: 1'b0 or 1'b1

.SRTYPE(SYNC) // Set/Reset type: SYNC or ASYNC

) ODDR_inst0 (

.Q(DataOut[0]), // 1-bit DDR output

.C(Clk), // 1-bit clock input

.CE(CE), // 1-bit clock enable input

.D1(DataIn[0]), // 1-bit data input (positive edge)

.D2(DataIn[8]), // 1-bit data input (negative edge)

.R(Reset), // 1-bit reset

.S(Set) // 1-bit set

);

雙邊緣輸入，單邊緣輸出：

IDDR #(

.DDR_CLK_EDGE(OPPOSITE_EDGE), // OPPOSITE_EDGE, SAME_EDGE

// or SAME_EDGE_PIPELINED

.INIT_Q1(1'b0), // Initial value of Q1: 1'b0 or 1'b1

.INIT_Q2(1'b0), // Initial value of Q2: 1'b0 or 1'b1

.SRTYPE(SYNC) // Set/Reset type: SYNC or ASYNC

) IDDR_inst1 (

.Q1(DataOutL[1]), // 1-bit output for positive edge of clock

.Q2(DataOutH[1]), // 1-bit output for negative edge of clock

.C(Clk), // 1-bit clock input

.CE(CE), // 1-bit clock enable input

.D(DataIn[1]), // 1-bit DDR data input

.R(Reset), // 1-bit reset

.S(Set) // 1-bit set

);