GTS Ethernet Intel® FPGA Hard IP User Guide

ID 817676
Date 7/08/2024
Public
Document Table of Contents

4.5.1.1. Insert Alignment Marker

The fabric controls the timing of alignment Marker insertion, and alignment markers cannot be delayed without disrupting the Ethernet link. For alignment marker counts, you only use valid cycles. When i_tx_mii_valid is low, the alignment marker counters and input data must freeze.

Figure 39. Inserting Alignment Markers
The number of cycles for i_tx_mii_am to remain high depends on the rate of the interface, Specifically:
  • 25GE with RS-FEC: 4 cycles
The number of cycle for AM period depends on the rate of the interface and whether in simulation or hardware. In simulation, its common to use a reduced AM period for both sides of the link is commonly used to increase lock-time speed. Specifically:
  • 25GE with RS-FEC: 2552 (Non - PTP design)
  • 25GE with RS-FEC: 5112 (PTP Design)
In hardware: 25GE with RS-FEC: 81920