F-Tile Low Latency Ethernet 10G MAC Intel® FPGA IP User Guide

ID 720985
Date 5/18/2023
Public

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7.9.3. PTP Register Configuration

Perform the following steps once after power up or link down event to calculate TX and RX datapath delay:
  1. Wait until the link is up and stable.
  2. Wait until tx_measure_valid and rx_measure_valid from 1G/2.5G/5G/10G Multirate Ethernet PHY IP register 0x420 are valid.
  3. Read TX and RX datapath deterministic latency values from the Multi-rate Ethernet PHY IP ptp_dl_tx and ptp_dl_rx registers, with offset 0x421 and 0x422 respectively and calculate TX/RX latency. Refer to Calculating Deterministic Latency.
  4. Convert the latency values to 16-bit nanoseconds and 16-bit fractional nanoseconds by multiplying the values by 216 or 65536.
  5. Calculate the sum of the latency values and the TX/RX PMA delay values (In nanoseconds and fractional nanoseconds).
  6. Write the total sum of TX and RX datapath delay to the Low Latency Ethernet 10G MAC static timing adjustment registers:
    1. Write the lower 16-bit TX values to 0x0102 register (TX fns value).
    2. Write the upper 16-bit TX values to 0x0104 register (TX ns value).
    3. Write the lower 16-bit RX values to 0x0122 register (RX fns value).
    4. Write the upper 16-bit RX values to 0x0124 register (RX ns value).