Altera 10-Gbps Ethernet MAC MegaCore Function - Manual (Page 76)

Chapter 7: Functional Description 7–9
Transmit Datapath
February 2014 Altera Corporation 10-Gbps Ethernet MAC MegaCore Function User Guide
7.4.5. Inter-Packet Gap Generation and Insertion
The MAC TX maintains an average IPG between transmit frames as required by the
IEEE 802.3 Ethernet standard. The average IPG is maintained at 96 bit times (12 byte
times) using the deficit idle count (DIC). The MAC TX's decision to insert or delete
idle bytes depends on the value of the DIC; the DIC is bounded between a minimum
value of zero and maximum value of three. Averaging the IPG ensures that the MAC
utilizes the maximum available bandwidth.
7.4.6. SDR XGMII Transmission
To comply with the IEEE 802.3 Clause 46 Ethernet standard, the MAC TX ensures the
following when transmitting frames on the SDR XGMII:
■ Aligns the first byte of the frame to either lane 0 or lane 4 of the interface.
■ Performs endian conversion. Transmit frames received from the client on the
Avalon-ST interface are big endian. Frames transmitted on the SDR XGMII are
little endian; the MAC TX therefore transmits frames on this interface from the
least significant byte.