Our world is becoming smarter and more connected, with buildings and factories being automated in unprecedented ways. To ensure these new systems operate effectively, reliable information
communication is essential – not only within industrial control panels, but also between various devices throughout the facility.
Until recently, industrial networks were complex and could require the use of a variety of protocols and gateways. This could be expensive, unreliable, and difficult to ensure the expected interoperability.
However, with the advent of 10BASE-T1S Ethernet, a change is happening. This innovative standard replaces legacy fieldbus technology, provides a variety of benefits for modern network environments,
and eliminates the need for gateways.
A range of devices supporting the new standard, such as ON Semiconductor's industrial 10BASE-T1S Ethernet controllers, provide a reliable and effective single-chip solution for connecting twisted pair
(TP) cables.
While the distances within industrial cabinets are relatively short, providing reliable connections in industrial applications can be challenging, especially due to the large amount of electrical noise
present. Large switchboards, motors, and many other high-current/high-voltage devices all generate some level of electromagnetic interference that can disrupt network communications.
In office applications, slow data transfer due to interruptions can be frustrating or inconvenient. However, in industrial applications, timely data transfer is critical, especially data from remote sensors
that control the operation of machinery. If the data is delayed or incorrect, process parameters may be violated or, worse, production equipment may be damaged.
For the same reason, timely data transfer becomes particularly important. This does not apply to protocols that negotiate bus access based on random timeouts.
Network infrastructure is often described as a "stack" with the physical implementation (wiring/media) at the bottom and increasingly complex software above it. In Factory 4.0 applications, artificial
intelligence (AI), machine learning (ML), planning, execution, automation, tracking, inventory control, supervisory control, etc. are at the top. The bottom layer (physical layer) is the factory floor, where
edge nodes including robots, actuators, motion sensors, and valves perform physical manufacturing work, often covering multiple assembly lines.
Communication at the top of the stack is typically over a multi-gigabit Ethernet LAN. However, communication on the factory floor is often a fragmented network of multipoint network fieldbus
protocols (including HART, RS-485, Mod-bus, DeviceNet, Profi-Bus, and CAN) over a pair of twisted pairs (possibly shielded wire or unshielded wire) operating at megabit speeds or less.
In order for it to work as a unified network, gateways need to be installed between the Ethernet portion and other protocols, which fragments communications and increases cost and complexity. A new
type of Ethernet will significantly enhance edge connectivity in smart building and factory applications.
The ratification of the IEEE 802.3cg specification in 2019 brought 10BASE-T1S. This standard is based on standard Ethernet, but has several important differences, providing 10Mb/s throughput,
multipoint operation with deterministic conflict handling. The standard operates over unshielded single twisted pair (SPE), greatly simplifying the installation process and reducing costs.
Deterministic operation is critical for real-time systems because real-time systems must transmit information within a known time. The CSMA/CD (Carrier Sense Multiple Access/Collision Detection)
used by traditional Ethernet uses random time periods, so the certainty of communication time cannot be guaranteed.
10BASE-T1S uses a new system called PLCA (Physical Layer Collision Avoidance) to avoid data collisions on the bus. Under PLCA, node 0 (the coordinator) sends a 2.0µs beacon to synchronize various
nodes in the network. Then, node 0 gets a transmission opportunity. If no data is transmitted, the opportunity is delivered to node 1 within the default standard 3.2 microseconds. In this cycle, each
node gets a sending opportunity in turn. After the cycle ends, the coordinator sends a beacon signal and a new cycle begins. If a node attempts to transmit more data than the allowed frame size, the
"jabber" function interrupts the transmission and passes the transmission opportunity to the next node, ensuring that the bus is not blocked.
By using PLCA, the worst-case media access delay can be calculated as the product of the current number of nodes and the maximum network frame size, which can be adjusted.
Many industrial applications are located in harsh electromagnetic environments, with switchgear, motors, and other large equipment generating radiated and conducted noise. Despite using unshielded
twisted pair cabling, 10BASE-T1S offers superior electromagnetic compatibility (EMC) performance compared to existing Ethernet protocols.
This is partly due to the application of PLCA. Because the bus is known to be collision-free, physical layer receivers are able to use complex algorithms to detect or recover signals when high levels of
noise are present in the environment.
With the introduction of the 10BASE-T1S protocol, new devices are optimized for 10BASE-T1S, allowing designers to take advantage of new features. For example, ON Semiconductor's NCN26010 is an
IEEE 802.3cg standard Ethernet transceiver that integrates a media access controller (MAC), PLCA reconciliation sublayer (PLCA-RS) and 10BASE for industrial multipoint Ethernet -T1S physical layer. The
device has built-in all physical layer functions required to send and receive data over a single unshielded twisted pair.
Despite integrating MAC, PLCA and PHY (including TX+RX), the device can be packaged in a small 4mm x 4mm QFN32 package and only requires a single 3.3V power supply. Its timing is driven by an
external 25MHz crystal oscillator or an external 25MHz clock source. Communication with the host is carried out through the OA SPI interface defined by the Open Alliance.
In addition, the NCN26010 also has an enhanced noise immunity (ENI) function, which can improve the noise immunity to a level higher than that required by the 10BASE-T1S specification. This greatly
improves network performance in noisy industrial environments.
In April 2024, ON Semiconductor released the NCN26000 10BASE-T1S Ethernet transceiver (PHY) designed for industrial Ethernet. It has many similarities with the earlier NCN26010, including compliance with the IEEE802.3cg standard, which can achieve multi-point, half-duplex 10 Mb/s data transmission rate through SPE.
The main difference between the two devices is that the NCN26000 contains only the PLCA-RS and PHY (TX + RX) in a 5mm x 5mm QFN package. The NCN26000 also requires a 3.3 V power supply and
a 25MHz external clock.
The NCN26000 has a Media Independent Interface (MII) that complies with the IEEE802.3 standard and can be connected to any CSMA/CD half-duplex capable MAC with CRS and COL pins. The MII can
also be used to configure and monitor the device (called MDIO).
Both devices integrate ON Semiconductor's ENI functionality, which significantly improves the performance of 10BASE-T1S multipoint applications in electrically noisy environments. When tested in the
lab, both devices easily exceeded the minimum requirement of 8 nodes within 25 meters. In fact, further testing showed that ENI can support approximately 40 nodes at 25 meters, 16 nodes at 50 meters, and 6 nodes at 60 meters, easily exceeding the requirements of the IEEE specification.
Not only does 10BASE-T1S feature deterministic operation, it is based on unshielded single-pair Ethernet (SPE) cables and is relatively low-cost to deploy. The lower cost and simpler integration of
10BASE-T1S helps bring a wide range of possibilities to applications that were previously limited by budget or packaging. One example is in complex industrial automation by upgrading previously
independent sensor nodes to connect them to centralized network systems. Previously available connectivity methods may have been too expensive or difficult to integrate, but 10BASE-T1S overcomes
these barriers. Similar cost and packaging challenges are encountered during the design of new robotics or automation solutions, and 10BASE-T1S can again help achieve higher interconnectivity without compromising performance or increasing budgets.
As the field of building automation continues to evolve, 10BASE-T1S can be used in applications such as control panels, human machine interfaces (HMI), sensors, actuators and lighting to provide a
high-speed and reliable backbone for the entire building.
In industrial applications, performance and cost are important, but noise immunity is particularly important. Here, 10BASE-T1S can be used to connect from control cabinets to programmable logic
controllers (PLCs), sensors, contactors and any other device suitably equipped with a 10BASE-T1S interface.
Until recently, automated factory networks required the installation of many gateways between edge devices and the main Ethernet network due to the incompatibility of the various protocols commonly used by edge devices. Typically, these fieldbus protocols include HART, RS-485, Mod-bus, DeviceNet, Profi-Bus, and CAN, each requiring its own gateway. This adds cost and complexity, especially since each gateway requires software updates and maintenance.
