F-Tile Architecture and PMA and FEC Direct PHY IP User Guide

ID 683872
Date 4/07/2025
Public
Document Table of Contents

A.5.4.1. F-Tile FGT NRZ Tuning Flow

In the tuning examples, BER and FOM are used as figures of merit. For FEC designs you can use the correct symbol rate as one more figure of merit. The following figure displays the recommended F-Tile FGT tuning flow.
Figure 167. F-Tile FGT Flowchart to Find Optimal TX Equalization Settings

BER is the Bit Error Rate. It is the primary figure of merit.

FOM is an indication of the vertical eye opening as it is updated during adaptation. It is a figure of merit used when auto adaptation is ON since it relies on auto adaptation firmware. If auto adaption is OFF, FOM cannot be used. FOM is a very fast vertical eye measurement and it is not the same as vertical eye height. The larger the FOM value, the larger the eye opening. Negative FOM value implies a failure of adaptation.

Eye Height value is in mV and can be used when auto adaptation is ON. In the attached tuning tcl script, for NRZ signaling, there is one eye height value readout. For PAM4 signaling, there are multiple eye height readouts; top eye height, middle height, and bottom eye height readouts.

Corrected symbol rate is for FEC based designs. It is calculated by using the corrected symbol number divided by the transmitted bits.
Table 128.  Signal Metrics Analysis
Figure of Merit Read/Write Registers and Sequence Description
BER Read/Write Refer to FGT Attribute Access Sequence for BER measurement Refer to tcl script for complete implementation.
FOM Read/Write Refer to FGT Attribute Access Sequence for FOM, VGA, CTLE Refer to tcl script for complete implementation.
Eye height Read/Write Refer to FGT Attribute Access Sequence for Eye Height measurement Refer to tcl script for complete implementation.
Corrected symbol rate with FEC Read Only

0x194

0x198

Refer to tcl script for complete implementation.

Refer to F-Tile Ethernet Intel FPGA Hard IP Register Map for more information.

To find the optimal RX equalization settings, you can use the tuning script in Example 3 : F-Tile FGT 5 Gbps NRZ Design .