E-Tile Transceiver PHY User Guide

ID 683723
Date 9/30/2022
Public
Document Table of Contents

7.12.1.1. Switching Between Any Two refclk[0, 1, 2, 3, 4, 5, 6, 7] Reference Clocks or Changing the Reference Clock Frequency on refclk[0, 2, 3, 4, 5, 6, 7, 8]

  1. Device configuration defaults the reference clock to refclk_in_A.
  2. Bring up refclk_in_B (refclk[1]), and switch PMA Mux to refclk_in_B (PMA Mux is now working on refclk_in_B (refclk[1]).
    • Make sure the refclk_in_B (refclk[1]) frequency is valid per the data sheet.
    • Write PMA attribute 0x30 = 0x3 to switch the PMA Mux.
  3. Switch Reference Clock Mux (9:1 mux) based on your requirement, or change the reference clock frequency (PMA Mux is still working on refclk_in_B (refclk[1]). For changing the reference clock frequency:
    1. If the old and new frequencies are both in the same range of 125-500 MHz or both in the same range 500-700 MHz, you only need to switch one reference clock from the old value to the new value.
    2. If, however, you are switching between 0-500 MHz and 500-700 MHz, you must use two reference clocks to represent the old and new clock frequencies, respectively.
  4. Bring up refclk_in_A, and switch PMA Mux to refclk_in_A.
    • Write PMA Attribute 0x30 = 0x0 to switch the PMA Mux.
  5. Perform a PMA Analog Reset.

Reference Clock Switch from refclk[0] to refclk[1]

refclk[0] Frequency Change from 156 MHz to 183 MHz

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