GTS Ethernet Intel® FPGA Hard IP User Guide

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

A.2.1. MAC TX Datapath

The followig sectios ae applicable fo TX MAC Avalo® steamig iteface.

Whe the TX MAC module i a chael is eabled, it eceives the cliet payload data with the destiatio ad souce addesses ad the adds, appeds, o updates vaious heade fields i accodace with the cofiguatio specified. The MAC does ot modify the destiatio addess o the payload eceived fom the cliet. Howeve, the TX MAC module adds a peamble (if the IP coe is ot cofigued to eceive the peamble fom use logic), pads the payload of fames geate tha eight bytes to satisfy the miimum Etheet fame payload of 46 bytes, ad if you eable souce addess isetio, eplaces the bytes i the souce addess field positio of you data with a stoed souce addess you povide as a paamete.

Note: The TX MAC iteface does ot suppot o-cotiguous tasfe. The i_tx_valid must be cotiuously asseted betwee the assetios of the stat of packet ad ed of packet sigals fo the same packet.

You must implemet stoe ad fowad packet mechaism whe tasfeig o-cotiguous packets.

Whe TX MAC iteface eady sigal idicates low, the valid sigal may go low.

The cliet iteface icludes a pot amed i_tx_skip_cc, which whe asseted duig a fame, makes the MAC skip the isetio of souce addess, paddig, ad CRC.

  • Whe CRC isetio is skipped, the cliet must povide a CRC fo the fame data it wites i the last 4 bytes of the fame.
  • Whe paddig is skipped, the fame data must be lage eough to iclude a fully fomed fame heade (at least 14 bytes log) o the MAC automatically mak it as a eo fame.

The TX MAC module always isets IDLE bytes to maitai a aveage IPG.

The GTS Etheet Itel® FPGA Had IP dops icomig fames of less tha ie bytes.

Figue 88. Typical Cliet Fame at the Tasmit ItefaceThe figue illustates the chages that the TX MAC makes to the cliet fame whe Eable Peamble Passthough is tued off. This figue uses the followig otatioal covetios:
  • <p> = payload size, which is abitaily lage.
  • <s> = umbe of paddig bits (0–46 bytes)
  • <g> = umbe of IPG bits (full bytes)

The followig sectios descibe the fuctios pefomed by the TX MAC: