Ethernet Design Example Components User Guide

ID 683044
Date 4/01/2024
Document Table of Contents IOPLL and TOD Setup using Dynamic Phase Shift Interface

To set up the IOPLL with dynamic phase shift interface and enable pulse per second (advanced accuracy mode) on a TOD Clock running on 125MHz period clock for Agilex™ 7 device, follow these steps:

  1. Create an Quartus® Prime project with Agilex™ 7 device selected.
  2. From IP Catalog, select IOPLL Intel FPGA IP.
  3. In IP Parameter Editor, apply the following settings and generate the IOPLL instance:
    1. Use the same clock source as TOD period_clk to drive IOPLL reference clock. Thus, set Reference Clock Frequency to 125 MHz.
    2. For Output Clocks section, set Number of Clocks to 2.
      1. Outclk0: Generate pps_sampling_clk, set Desired Frequency to 85.33MHz (pps_sampling_clk = period_clk *256/375). Sampling clock factor of 256/375 is suitable for all supported period_clk frequencies.
      2. Outclk1: Second clock port of the IOPLL must be allocated for TOD iopll_phased_clk. Set Desired Frequency to the same as TOD period_clk frequency (125MHz).
    3. In the same Output Clocks section, enable Specify VCO frequency and set Desired VCO Frequency to 1375 MHz.
      • Intel recommends you to specify the VCO frequency value as this value is used to determine PLL unit phase shift parameter value of TOD. Otherwise, you can refer to Advanced Parameters tab for auto assigned VCO frequency.
    4. At Dynamic Reconfiguration tab, select Enable access to dynamic phase shift ports.
  4. From IP Catalog, select Ethernet IEEE 1588 Time of Day Clock Intel FPGA IP.
  5. In IP Parameter Editor , apply the following settings and generate the TOD Clock instance:
    1. De-select Enable high clock frequency mode
    3. Set DEFAULT_FNSEC_PERIOD to 0x0
    6. Select Enable pulse per second interface
    7. Select Advanced for Accuracy mode
    8. Enter desired value for Pulse width.
    9. Enter “100” for PLL scan clock frequency. This example uses 100 MHz as clock for iopll_scan_clk.
    10. Enter “90” for PLL unit phase shift. This example has set IOPLL VCO frequency to 1375 MHz, the unit phase shift equals to 1/8 of IOPLL VCO period, thus 90 ps.
    The diagram below illustrates the connection between IOPLL and TOD instances. Note that the diagram does not elaborate on all interfaces of the TOD instance.
    Figure 1.  Example of connections between IOPLL Interface and TOD Clock’s Advanced Accuracy Pulse Per Second Interface