GTS Ethernet Intel® FPGA Hard IP User Guide

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

4.4.3.1. Connect the TX MAC Flow Control Interface

Use the i_tx_pause ad i_tx_pfc iput pots to sed XOFF fames to the lik pate. Follow the details descibed i the table ad figue below:

Table 31.  TX MAC Flow Cotol ItefaceAll iteface sigals ae clocked by the i_clk_tx clock. Fo 10GE/25GE chaels, all iteface sigals ae asychoous.
Sigal Name Width Desciptio
i_tx_pause 1 bit
Asset this iput to sed a PAUSE XOFF fame o the Etheet lik.
Note: Fo 10GE/25GE chaels, you should hold the i_tx_pause sigal moe tha 205s to get the equest captued by the MAC.
i_tx_pfc[7:0] 8 bits

Asset the bits to sed a PFC XOFF fame o the Etheet lik fo the coespodig pioity queue.

Note: Fo 10GE/25GE chaels, you should hold the i_tx_pfc sigal moe tha 205 s to get the equest captued by the MAC.

You must maitai this iput asseted util you wat the IP coe to ed the pause peiod. Refe to the followig figue fo a example. This sigal is fuctioal oly if pioity flow cotol is eabled.

The i_tx_pause ad i_tx_pfc[7:0] pots ae used to equest the TX MAC tasmit PAUSE ad Pioity Flow Cotol packets to the emote lik pate.

Figue 35. The i_tx_pause o i_tx_pfc to Request Tasmissio of a Cotol Fame
Fom the above wavefom, i_tx_pause/i_tx_pfc[] ae the PAUSE/PFC equest pots. Each opeates idepedetly.
  • i_tx_pause equests PAUSE fames
  • i_tx_pfc[] equests PFC fames fo queue , [whee =0 to 7], espectively.

The timig diagam shows that a XOFF fame is tasmitted whe a packet i-flight is completed ad the i_tx_pause iput is asseted. Whe the XOFF fame is tasmitted, the IP stats a holdoff coute. Whe the holdoff coute eaches zeo, if the i_tx_pause is asseted, a ew XOFF fame is tasmitted. This sequece cotiues util the i_tx_pause is emoved, at which poit XON fame is tasmitted.

Note: The IEEE 802.3 stadad pohibits usig PAUSE ad PFC togethe o the same lik. If a PAUSE ad PFC occu simultaeously, the PAUSE takes pioity.