40- and 100-Gbps Ethernet MAC and PHY MegaCore Function User Guide

ID 683114
Date 6/15/2022
Public
Document Table of Contents

3.4.1.17. MAC Feature Configuration Registers

The MAC feature configuration registers control the following additional MAC features in the RX and TX datapaths:

  • Padding configuration
  • Preamble pass-through feature
  • Inter-packet gap adjustment
Table 62.  MAC Feature Configuration Registers 

Address

Name

Bit

Description

HW Reset Value

Access

0x124

PAD_CONFIG

[0]

When set to 1, the IP core removes padding from frames on the RX datapath. When you set this bit to the value of 1, the IP core disables the CRC_CONFIG (register 0x123 bit [1]) from having any effect on padded packets.

0

RW

0x125

Preamble Pass-Through Configuration

[1]

Enable TX preamble pass-through. This bit has the following valid values:

  • 1’b0: Disable TX preamble pass-through.
  • 1’b1: Enable TX preamble pass-through.

1’b0

RW

[0]

Enable RX preamble pass-through. This bit has the following valid values:

  • 1’b0: Disable RX preamble pass-through.
  • 1’b1: Enable RX preamble pass-through.

1’b0

RW

0x126

IPG_DEL_PERIOD

[11:0]

If IPG_DEL_ENABLE[0] has the value of one, the IPG_DEL_PERIOD register controls the frequency of Idle byte deletion from the default inter-packet gap Idle sequence.

If IPG_DEL_ENABLE[0] has the value of one, and IPG_DEL_PERIOD[11:0] has the value of N, the MAC deletes extra Idle bytes from the inter-packet gap in the ratio of one Idle byte for every N 8-byte blocks.

At the default value of 2048, this deletion compensates for Alignment Marker insertion by the PHY (approximately 61 ppm). You can modify the value of this register field to increase bandwidth or adjust for clock compensation, as needed.

12’d2048

RW

0x127

IPG_DEL_ENABLE

[0]

Enables the inter-packet gap adjustment feature. If this bit has the value of 1, the MAC deletes inter-packet gap Idle bytes at the frequency specified in the IPG_DEL_PERIOD register.

If this bit has the value of 0, the MAC does not implement the inter‑packet gap adjustment feature, but instead, generates the usual inter‑packet gap, to an average IPG of 12 bytes.

1’b1

RW