Overview

This page lists the software features and protocols supported by the MCU Plus SDK Ethernet (CPSW) drivers

Feature Summary

Feature	Description
Basic L2 Switching	Ethernet packet switching with 10M/100M/1G Bandwidth with Multicast and VLAN Capability
L3 switching with LwIP Stack	TCP/IP and UDP protocol integration with LwIP
TSN support	gPTP protocol stack support for Time Synchronization
EST/TAS support	IEEE 802.1Qbv compliant traffic scheduling capabilities
CBS	IEEE 802.1Qav compliant traffic shaping feature supported in Enet-lld driver
IET	IEEE 802.3br compliant frame preemption feature supported in Enet-lld driver
Cut Through	IEEE 802.1DU compliant Packet forwarding without store and delay supported

Basic Layer 2 Switching

Common Platform Switch or CPSW supports Layer 2 Ethernet packet switching on 10M/100M/1G bandwidth in Half or Full Duplex mode (Half Duplex with 1G is not supported) on both of its external MAC ports. CPSW operates in two modes, namely:

Switch Mode - packet forwarding is enabled and packets are forwarded to Host + Other MAC ports. This is the default configuration for CPSW.
MAC mode - packets are only given to the Host port and are not forwarded to other MAC Ports.

The switch dynamically builds and maintains a forwarding table to optimize traffic flow within the network using its Address Learning Engine submodule, which also gives the flexibility of auto-ageing the learnt entries.

It is capable of handling IEEE 802.1Q compliant Virtual LAN tagged packets.
Multicast traffic handling is supported.
This SDK includes out-of-the-box examples of MAC and PHY Loopback capability. For further details, refer to Enet CPSW Loopback Example
SDK also includes a 'vanilla' L2 CPSW switch example. For further details, refer to Enet Layer 2 CPSW SWITCH Example

For further driver details and IOCTLs, refer to Enet-LLD

Layer 3 switching with LwIP Stack

TCP/IP and UDP protocol stacks are provided by the open-source Lightweight IP (LwIP) stack. The SDK integrates all major L3 and above protocols such as TCP, UDP, ICMP, ARP, DHCP, and HTTP with IPv4.

CPSW is capable of packet routing based on IP addresses, both with and without VLAN.
Hardware is also capable of TCP/UDP checksum offload. UDP-Lite checksum offload is performed in driver software.

The SDK provides a set of default parameters (such as LwIP pbuf memory pool size) for LwIP integration for every SoC that can be configured per requirement. The SDK also provides numerous examples with the LwIP stack; the following table lists a few of them:

Example	Reference
TCP server	Enet Lwip TCP Server Example on CPSW
TCP Client	Enet Lwip TCP Client Example
UDP Client	Enet Lwip UDP Client Example
UDP IGMP	Enet Lwip UDP IGMP Server Example
Lwip Sockets	Enet Lwip Socket Example
Iperf testing	Enet Lwip CPSW Example
HTTPS Server	CPSW Lwip HTTPS Server Example

TLS support is enabled for examples such as HTTPS using the open-source MbedTLS library. This feature provides encryption, authentication, and data integrity protection for network traffic. For further reading about MbedTLS, see https://mbed-tls.readthedocs.io/en/latest/

Note: Currently IPv6 is not supported by the driver.

For further details please check Lightweight IP (LwIP)

TSN support

SDK provides general Precision Time Protocol(gPTP) or IEEE 802.1AS stack enabled for time synchronization across networked devices. It establishes a common time reference with sub-microsecond accuracy, allowing coordinated operation of distributed systems. Accurate synchronization is critical for scheduled traffic, industrial automation, and time-sensitive networking applications. The protocol continuously compensates for clock drift and network delays to maintain timing precision.

The CPTS submodule of CPSW is used for timestamping packets, and Time Sync IOCTLs provide a way to configure it.

The SDK gives full fledged gPTP example in

gPTP variant	Reference
Master mode	Ethernet TSN CPSW gPTP TimeTransmitter (gPTP Master) Example
Slave mode	Ethernet TSN CPSW gPTP TimeReceiver (gPTP Slave) Example
Bridge mode	Ethernet TSN CPSW gPTP Bridge Example
Parallel to LwIP stack	Ethernet TSN gPTP on CPSW along with LwIP stack

For further details, read Ethernet TSN and gPTP Stack - API and Integration Guide

EST/TAS support

Enhanced Scheduled Traffic (EST), also known as Time-Aware Shaper (TAS), provides IEEE 802.1Qbv compliant traffic scheduling capabilities. CPSW supports express traffic of 8 priority classes and generates a repeating open-close sequence for the gates of each priority class via the CPTS EST function generator. It can be configured to work with or without preemption. This enables deterministic transmission windows for time-critical traffic. Gate control schedules ensure that high-priority frames are transmitted at precisely defined times. This feature is essential for real-time industrial and automotive networking applications.

The SDK provides a menu-driven example with positive and negative test cases for configuring various gate sequences to demonstrate this feature. The example is described in detail here: Enet CPSW EST Example
EST related IOCTLS are described here Enet Time Aware Shaper API

CBS

Credit-Based Shaper is defined by IEEE 802.1Qav. Its primary purpose is to smooth out bursty traffic by distributing data transmissions evenly over time, thereby providing a deterministic upper bound on network latency and preventing high-priority streams from completely blocking lower-priority traffic. The CBS algorithm works by assigning a credit counter to each high-priority traffic queue. Packets can only be sent if the queue's credit balance is greater than or equal to zero. When a high-priority queue has data waiting to be sent, but is blocked because a lower-priority packet is currently occupying the physical wire, it accumulates credit at a defined rate called the idleSlope. While the high-priority queue is actively transmitting its data, its credit balance decreases at a rapid rate called the sendSlope.

This feature is implemented in the driver, but no example currently demonstrates this feature. The list of IOCTLs that implement this is provided below:

IET

Interspersing Express Traffic (IET) is specified in IEEE 802.3br. It reduces latency for critical time-sensitive data by allowing high-priority frames to temporarily interrupt (preempt) an ongoing, lower-priority frame mid-transmission. Once the urgent packet is sent, the interrupted frame automatically resumes without having to be entirely retransmitted, preventing large best-effort data packets from blocking critical control streams. This mechanism is particularly beneficial for deterministic and real-time communication systems.

This feature is implemented in the driver, but no example currently demonstrates this feature. The list of IOCTLs that implement this is provided below:

Cut Through

Cut-Through Forwarding is defined by IEEE 802.1DU. Cut-through switching is a network packet forwarding method where a switch minimizes latency by transmitting a frame before it is completely received. Unlike traditional store-and-forward switching, which waits for the entire packet to arrive, a cut-through switch reads only the destination address and immediately starts routing the data. Any received packets with errors that are sent through cut-through from an Ethernet receive port to any Ethernet transmit port(s) will egress with at least one byte of the generated outgoing packet CRC inverted to indicate the error. This occurs because cut-through operations begin before the end of the packet when the receive port detects that the packet had an error.

In this SDK Enet Layer 2 CPSW SWITCH Example uses the Cut-Through feature.

The list of IOCTLs that implement this is provided below:

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