GTS Ethernet Intel® FPGA Hard IP User Guide

ID 817676
Date 10/12/2024
Public
Document Table of Contents

4.1.4. Implement Clock Connections in Synchronous Ethernet Operation (Sync-E)

Whe you eable the Sychoous Etheet (Syc-E) mode, two o moe chaels ca shae the off-chip cleaup PLL clock output. The Sychoous Etheet stadad, descibed i the ITU-T G.8261, G.8262, ad G.8264 ecommedatios, equies that the TX clock be filteed to maitai sychoizatio with the RX efeece clock though a sequece of odes. You must dive the tasceive efeece clocks with a filteed vesio of the RX ecoveed clock sigal, to esue the eceive ad tasmit fuctios emai sychoized. I this sceaio, a desig compoet outside the IP pefoms the filteig.

Figue 17. Clock Coectio of Syc-E Clock Though CDR Clock Out Pi

The diagam above shows the clockig equiemet to eable SycE opeatio. The ecoveed clock outputs o_clk_ec_div o o_clk_ec_div64 o o_cd_divclk fom the GTS Etheet Itel® FPGA Had IP ae coected to the off-chip cleaup PLL usig the REFCLK_GTS pi. The dedicated clock output (o_cd_divclk) fom the PMA ca be dive to a local efeece clock pi o dedicated clock output pis if the device has sigle tasceive bak, wheeas the clocks o_clk_ec_div64 ad o_clk_ec_div ae available at GPIO pis.

Fo moe ifomatio about the suppoted pis, efe to Pi Coectio Guidelies: Agilex™ 5 FPGAs ad SoCs.

Two o moe chaels shae the clock output of a Off-chip Cleaup PLL that meets the specificatio fo a SycE lik. The FPGA povides a pimay SycE clock ad a backup SycE clock to the cleaup PLL. The pimay ad backup cleaup clocks come fom ecoveed clock output pis fom a pai of chaels that ae both coected to emote statios coected to the same SycE etwok, with the tasceive efeece clock souced fom the output of the cleaup PLL. Refe to the followig figue to eable the Syc-E optio:

Figue 18. Eable Syc-E optio i the IP Paamete Edito

The output fequecy is equal to the omial icomig i_clk_ef_p divided by ay pedivide o the RX path. The followig table shows the ecoveed clock fequecies with espect to iput efeece clock.

Table 20.  Recoveed Clock Fequecy
Data Rate Iput Refclk (MHz) N Divide Output Recoveed Clk (MHz)
10GE 156.25 1 156.25
312.5 2 156.25
322.265625 3 107.421875
25GE 156.25 4 39.0625
312.5 8 39.0625
322.265625 3 107.421875
Note: If the EHIP System clock is deived fom a diffeet efeece clock tha the tasceive, the set the IP to "System PLL" i “Custom Cadece” mode optio to match the PPM diffeece betwee the clocks. Fo Syc-E applicatios, the local oscillato must match the ecoveed clock withi +/-4.6ppm.