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

ID 683872
Date 11/04/2024
Public
Document Table of Contents

5.3. Implementing a RS-FEC Direct Design in the F-Tile PMA/FEC Direct PHY Intel® FPGA IP

To istatiate a RS-FEC diect desig, follow the steps metioed i sectio Istatiatig the F-Tile Refeece ad System PLL Clocks Itel FPGA IP. I additio to the PMA data path paameteizatio, a RS-FEC diect desig allows you to eable the RS-FEC mode fo fowad eo coectio i a NRZ o PAM4 desig cofiguatio.

The RS-FEC optio i F-Tile PMA/FEC Diect PHY Itel® FPGA IP suppots the RS-FEC modes specified i sectio FEC Achitectue. Also efe to F-Tile Suppoted FEC Modes ad Compliace Specificatios fo a compehesive list of RS-FEC modes i the F-Tile PMA/FEC Diect PHY Itel® FPGA IP. Additioally, efe to sectio FEC Placemet Rules fo ules to follow whe cofiguig a RS-FEC diect desig.

I the RS-FEC tab of the F-Tile PMA/FEC Diect PHY Itel® FPGA IP, you select the Eable RS-FEC to cofigue a desig with FEC as show i the followig figue.

Figue 107. Eablig RS-FEC Mode i the IP Paamete Edito

Based o the RS-FEC mode ad data ate fo you desig, you alig the PMA paallel clock fequecy ad choose the System PLL fequecy accodigly. Esue that the System PLL fequecy you choose i the F-Tile PMA/FEC Diect PHY Itel® FPGA IP aligs with the F-Tile Refeece ad System PLL Clocks Itel® FPGA IP efeece clock fequecy.

Thee ae additioal optios that you ca eable fo you RS-FEC desig. To eable the loopback select the Eable RS-FEC loopback optio. You ca also eable the Eable RS-FEC data iteleave patte optio. Whe you eable this optio, the RS-FEC laes ae bit-iteleaved o each physical lae by 64/80 bits. The default value is Off.

Whe you eable the RS-FEC featue i you desig, the TX ad RX deskew logic is eabled. Refe to sectio Deskew Logic fo moe ifomatio about the deskew logic i the TX ad RX datapath.

I a FEC diect desig, duig eset sequecig, afte tx_am_ge_stat is asseted, stat sedig the aligmet makes ad asset tx_am_ge_2x_ack afte two aligmet makes ae set. The tx_am_ge_stat goes high as pat of the eset sequece, befoe tx_eady is asseted. I additio, i the FEC diect mode, you ca pace the TX data valid sigal with the tx_cadece sigal.

Fo example, i the 100G FEC diect desig, the aligmet make (AM) cycle is 81920 clock cycles ad the AM pulse width is 5 clock cycles wide. I additio, the TX data is uscambled. If a FEC diect desig does ot lock o alig, the RX data is zeo.

The FEC had IP coe has a paamete that detemies the legth of the aligmet make peiod, ad is set to 10. The FEC had IP coe ot oly checks fo the AM peiod, but also fo the AM pulse width.
Table 112.  FEC Mode AM Pulse Width Duatio
FEC Mode AM Pulse Width (Numbe of Cycles at IP Iteface)
25G 4
50G 2
100G 5
128GFC, 200G, 400G 2
32GFC 1
64GFC 2

Whe FEC is cofigued i 200G o 400G vaiat modes, you should ot scamble o descamble the data as this is doe by the RS-FEC had IP. I all othe FEC cofiguatios, such as 25G, 50G o 100G, you have to scamble the iput data ad you have to descamble output data.