40- and 100-Gbps Ethernet MAC and PHY MegaCore Function User Guide

ID 683114
Date 6/15/2022
Public
Document Table of Contents

3.2.10. Pause Control Frame and Non‑Pause Control Frame Filtering and Forwarding

The 40GbE and 100GbE MAC IP cores can pass the pause packets through as normal traffic or drop the pause control frames in the RX direction. You can enable and disable pass-through with the following configuration control bits:

  • RX_FILTER_CTRL bit [4] enables and disables pause filtering.
  • RX_FILTER_CTRL bit [5] enables and disables control filtering.

By default, pass-through is disabled.

The following rules define pause control frames filtering control:

  1. The RX_FILTER_CTRL register contains options to filter different packets types, such as runt packets, FCS error packets, address mismatch packets, and so on, from the RX MAC. The RX_FILTER_CTRL register contains one bit to enable pause packet filtering and one bit to enable non-pause control packet filtering. The reset state for both bits is 1, where filtering is enabled. The bits are gated by RX_FILTER_CTRL bit [0], which enables and disables all filtering.
  2. If you have enabled pause packet filtering, the IP core drops packets that enter the RX MAC and match the length and type of 0x8808 with an opcode of 0x1 (pause packets) and does not process them or forward them to the client interface.
  3. If you have enabled non‑pause control packet filtering, the IP core drops packets that enter the RX MAC and match the length and type of 0x8808 with an opcode other than 0x1 (pause packets) and does not forward them to the client interface.
  4. If you have disabled pause packet filtering, the RX MAC forwards pause packets to the client interface depending on their destination address. If destination address filtering is not enabled, you are forwarded all pause packets. If destination address filtering is enabled, you are only forwarded pause packets with a valid packet multicast address or a destination address matching the 40‑100GbE IP core address.

Pause and control packet pass-through do not affect the pause functionality in the TX or RX MAC.