GTS Transceiver PHY User Guide: Agilex™ 5 FPGAs and SoCs

ID 817660
Date 8/04/2025
Public
Document Table of Contents

3.3.6.4. PMA Configuration Rules for GPON Mode

You can implement the GPON protocol mode with the GTS PMA/FEC Direct PHY IP by using the settings shown below:
  • Set the PMA configuration rules parameter to GPON.
  • Set the RX Adaptation mode parameter to manual.
  • Enable the rx_cdr_fast_freeze_sel port.
  • Enable the rx_cdr_freeze port.
To achieve the best RX performance when receiving the burst mode traffic, you must adhere to the following guidelines:
  • You must tie the i_rx_cdr_fast_freeze_sel signal to 1’b0.
  • You must assert the i_rx_cdr_freeze signal when the burst disappears and deassert the i_rx_cdr_freeze signal when the burst appears.
  • During the idle time (no active burst), the differential voltage at the RX should be 0 instead of a positive/negative value. This is to ensure the AC coupling capacitor can quickly charge up to a stable value when the burst arrives.
  • You must manually tune the RX EQ parameters: VGA gain, high frequency boost and DFE data tap 1.
Note: When the other parameters are fixed, a smaller RX input voltage swing requires a smaller VGA gain value. A larger RX input voltage swing requires a larger VGA gain value.