LVDS接口总结--(5)IDELAY3仿真

仿真参考资料如下：

https://zhuanlan.zhihu.com/p/386057087

`timescale 1 ns/1 ps
module tb_idelay3_ctrl();
    parameter	REF_CLK		=  2.5        ;  // 400MHz
    parameter	DIN_CLK	    =  3.3        ;  // 300MHz

    reg			                ref_clk     ;
    reg			                clk_din     ;
    reg			                rst     ;
    wire                        din     ;
    reg   [8 : 0]               cntvaluein;
    wire  [8 : 0]               cntalueout  ;
    wire                        rdy         ;
    wire                        dout        ;
    reg   [15 : 0]              test_pattern = 16'h0c55;
    reg   [3 : 0]               data_cnt = 4'h0;
    
    initial begin
        rst = 1;
        ref_clk = 0;
        clk_din = 0;
        #500;
        rst = 0;

    end
    
always #(REF_CLK/2)  ref_clk = ~ref_clk;
always #(DIN_CLK/2)  clk_din = ~clk_din;




    always @(posedge clk_din or posedge rst)begin
        if(rst)
              data_cnt <= 4'd0;
        else
              data_cnt <= data_cnt +1'd1;
        end
	

    assign	din = test_pattern[data_cnt];


    always @(posedge clk_din or posedge rst)begin
        if(rst)
              cntvaluein <= 9'd0;
        else if(data_cnt == 4'd15)
              cntvaluein <= cntvaluein +1'd1;
        else;
        end
    
     idelay3_ctrl  u_idelay_ctrl (
        .ref_clk    ( ref_clk       ),
        .rst        ( rst           ),
        .din        ( din           ),
        .cntvaluein ( cntvaluein    ),
        .cntalueout ( cntalueout    ),
        .rdy        ( rdy           ),
        .dout       ( dout          )
    );   
    		
endmodule

module idelay3_ctrl(
    input									ref_clk		    ,
    input									rst		    ,
    input				            	    din		    ,
    input       [8 : 0]                     cntvaluein  ,

    output      [8 : 0]                     cntalueout  ,
    output                                  rdy         ,
    output  	                            dout	     
    );

    
    
			
			
    
  IDELAYCTRL #(
      .SIM_DEVICE("ULTRASCALE")  // Set the device version for simulation functionality (ULTRASCALE)
   ) inst_IDELAYCTRL (
			.RDY(rdy), 					// 1-bit output: Ready output
			.REFCLK(ref_clk), 	// 1-bit input: Reference clock input
			.RST(rst) 		// 1-bit input: Active high reset input
			);	
			
			
   IDELAYE3 #(
      .CASCADE("NONE"),               // Cascade setting (MASTER, NONE, SLAVE_END, SLAVE_MIDDLE)
      .DELAY_FORMAT("TIME"),          // Units of the DELAY_VALUE (COUNT, TIME)
      .DELAY_SRC("IDATAIN"),          // Delay input (DATAIN, IDATAIN)
      .DELAY_TYPE("VAR_LOAD"),           // Set the type of tap delay line (FIXED, VARIABLE, VAR_LOAD)
      .DELAY_VALUE(0),                // Input delay value setting
      .IS_CLK_INVERTED(1'b0),         // Optional inversion for CLK
      .IS_RST_INVERTED(1'b0),         // Optional inversion for RST
      .REFCLK_FREQUENCY(400.0),       // IDELAYCTRL clock input frequency in MHz (200.0-800.0)
      .SIM_DEVICE("ULTRASCALE_PLUS"), // Set the device version for simulation functionality (ULTRASCALE,
                                      // ULTRASCALE_PLUS, ULTRASCALE_PLUS_ES1, ULTRASCALE_PLUS_ES2)
      .UPDATE_MODE("ASYNC")           // Determines whe     n updates to the delay will take effect (ASYNC, MANUAL,SYNC)
   )
   IDELAYE3_inst (
      .CASC_OUT(),       // 1-bit output: Cascade delay output to ODELAY input cascade
      .CNTVALUEOUT(cntalueout), // 9-bit output: Counter value output
      .DATAOUT(dout),         // 1-bit output: Delayed data output
      .CASC_IN(1'd0),         // 1-bit input: Cascade delay input from slave ODELAY CASCADE_OUT
      .CASC_RETURN(1'd0), // 1-bit input: Cascade delay returning from slave ODELAY DATAOUT
      .CE(1'b0),                    // 1-bit input: Active-High enable increment/decrement input
      .CLK(ref_clk),                 // 1-bit input: Clock input
      .CNTVALUEIN(cntvaluein[8:0]),   // 9-bit input: Counter value input
      .DATAIN(),           // 1-bit input: Data input from the logic
      .EN_VTC(!rdy),           // 1-bit input: Keep delay constant over VT
      .IDATAIN(din),         // 1-bit input: Data input from the IOBUF
      .INC(1'b0),                // 1-bit input: Increment / Decrement tap delay input
      .LOAD(1'b1),               // 1-bit input: Load DELAY_VALUE input
      .RST(1'b0)                  // 1-bit input: Asynchronous Reset to the DELAY_VALUE
   );

endmodule

|--------------------|------------|
| delay tap =0 | 127ps |
| delay tap =1 | 131ps |
| delay tap =2 | 135ps |
| delay tap =3 | 139ps |
| ... | 　 |
| delay tap =100 | 527ps |
| delay tap =200 | 927ps |
| delay tap =219 | 1003ps |
| delay tap =468 | 1999ps |
| delay tap =511 | 2171ps |

根据上表可知 delay_tap = 127 + 4N （N的取值为0到511）

根据简单的计算可知，双沿300M数据(对应单沿600M数据)，数据持续时间为1.66ns,取到中间需要0.83ns，对应177taps