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

ID 817660
Date 10/17/2025
Public
Document Table of Contents

3.3.6.4. PMA Configuration Rules for GPON Mode

You can implement the OLT (Optical Line Terminal)31 with the GPON protocol by using the following configuration settings in the GTS PMA/FEC Direct PHY IP:
  • 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 high-frequency boost and DFE data tap 1 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.
Note: FEC options and PCS options are not available for GPON mode. You must implement your own soft FEC/PCS logic.
Note: For GPON mode, you must enable the Avalon Memory-Mapped Interface and drive i_reconfig_clk. This is to ensure after device configuration, all the configuration registers are automatically set properly for GPON mode.
31 For ONU (Optical Network Unit) or ONT (Optical Network Terminal) implementation, GPON mode is not applicable. Instead, you should set the PMA configuration rule as Basic.