1、IBUFGDS输入全局时钟及DCM分频使用：

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单边缘与双边缘触发的转换。

单边缘输入双边缘输出：

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
);

双边缘输入，单边缘输出：

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
);

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