Data communication is playing an increasingly important role not only in industry but also in process automation. The previous 4 mA to 20 mA or fieldbus applications also began to encounter bottlenecks due to the explosion of data volume, so Ethernet began to become the communication standard. The standard 4-wire Ethernet solution has evolved into a 2-wire solution, which we call 10BASE-T1L, which consists of a single twisted pair or single-pair Ethernet (SPE). 10BASE-T1L sits on top of the physical layer and is compatible with existing 100 Mbps or 1000 Mbps Industrial Ethernet technology, so it can be used as a complement.

By Thomas Brand, Senior Field Applications Engineer, Analog Devices | Thomas Tzscheetzsch, Senior Field Technology Supervisor, Analog Devices

Summary

Many aspects of our daily lives depend on data communication between various devices. The proliferation of devices and the dramatic increase in data volumes brought about by digitization and Industry 4.0 are transforming the communications landscape. For example, areas such as process automation require the use of integrated networks to support plant-wide connectivity needs. We have to extract and process data from operational technology (OT) machines and then feed the processed data to computer systems (IT) at the company level for further processing. As previous 4 mA to 20 mA or fieldbus applications encountered bottlenecks in data communication, Ethernet began to become the communication standard. The first is the new Ethernet standard 10BASE-T1L, a 2-wire Ethernet solution with a line length of 1000 meters and a transmission speed of 10 Mbps, while supporting transmission protocols such as PROFINET, Ethernet/IP, OPC UA, Modbus-TCP, etc. Using this standard, we can continue to use our existing 2-wire cabling and avoid wasting our investment.

This article introduces the basics of 10BASE-T1L and showcases products related to selecting suitable connectors for various applications. Power transmission to various interconnected devices through data lines also plays a vital role in 10BASE-T1L.

Introduction

Data communication is playing an increasingly important role not only in industry but also in process automation. The previous 4 mA to 20 mA or fieldbus applications also began to encounter bottlenecks due to the explosion of data volume, so Ethernet began to become the communication standard. The standard 4-wire Ethernet solution has evolved into a 2-wire solution, which we call 10BASE-T1L, which consists of a single twisted pair or single-pair Ethernet (SPE). 10BASE-T1L sits on top of the physical layer and is compatible with existing 100 Mbps or 1000 Mbps Industrial Ethernet technology, so it can be used as a complement.

10BASE-T1L is starting to standardize, especially in process automation, and has the potential to revolutionize the field. Currently, sensors and actuators in this field are usually connected via 4 mA to 20 mA analog interfaces or fieldbuses. Unlike mechanical engineering or factory automation, the sensors and actuators of process automation are often at a distance from the control system or remote I/O system. Common distances are 200-1000 meters or more.

But what exactly is 10BASE-T1L, what are the advantages of this technology, and why is it the new standard?

We will answer these questions in subsequent sections.

What does 10BASE-T1L mean?

The name 10BASE-T1L roughly explains its meaning. The Institute of Electrical and Electronics Engineers (IEEE) abbreviation is used here.

The “10” in the media type refers to a 10 Mbps transfer rate. “BASE” refers to baseband signals, i.e. only Ethernet signals can be transmitted over the medium. “T” stands for “twisted pair”. The number “1” stands for 1 km range. In this case, the following “L” stands for “long distance”, meaning that the segment length may be 1 km or more.

In addition, other network technologies exist such as 10BASE-2 (thinner coaxial cable with a maximum segment length of 185 m), 10BASE-5 (thicker coaxial cable with a maximum segment length of 500 m), 10BASE-F (fiber optic cable ) or 10BASE-36 (broadband coaxial cable with multiple baseband channels and a maximum segment length of 3600 m).

In which layer of the OSI model is 10BASE-T1L classified?

10BASE-T1L can use existing 2-wire infrastructure with line lengths up to 1000 m and transmission speeds of 10 Mbps. Physical Ethernet technology is only defined at layer 1 (bit transport layer or physical layer) of the Open Systems Interconnection (OSI) model. 10BASE-T1L is on top of the bit transport layer and supports common Ethernet protocols (such as PROFINET, Modbus, etc.) and other bus systems commonly used in building management systems (such as BACnet, KNX and LON). Table 1 is an overview of the model layers and the protocol and bus system.

10BASE-T1L can be implemented with a special Ethernet PHY at Layer 1. Ethernet frames are transported between the MAC and the PHY through the Media Independent Interface (MII), Reduced MII (RMII), or Reduced Gigabit MII (RGMII).

The MAC is defined by the Ethernet standard IEEE 802.3 and implemented in the data link layer (layer 2). The PHY forms the physical interface and is responsible for encoding and decoding data between the transmission medium and the digital system.

What devices and machines can 10BASE-T1L be used with? To what extent can existing infrastructure work with it?

10BASE-T1L is designed to replace 4 mA to 20 mA standardized signals in many, if not most, process automation applications. However, this does not mean that older field instruments connected via a 4 mA to 20 mA current loop must be replaced with 10BASE-T1L capable field instruments. These legacy devices can be connected via software-configurable I/O (SWIO) modules, while remote I/Os are used as acquisition points to the PLC via a 10 Mbps Ethernet uplink.

Software-configurable I/O modules feature reconfigurable module channels, allowing modules to be operated quickly and easily remotely without extensive rewiring. Channels can be configured as current and voltage inputs or outputs, or digital and analog inputs or outputs.

In some cases, it is required to power devices and transmit device data via 10BASE-T1L, which is defined as part of the standard. Figure 1 shows an example of a mix of traditional field instruments connected through a 4 mA to 20 mA current loop and new field instruments supporting 10BASE-T1L.

Table 1. Overview of OSI models and their protocols and bus systems

OSI model layer

BACnet

Modbus

KNX

LON

host layer

7 | Applications

BACnet application layer

Modbus

KNX

LON

6 | Showcase


5 | Session


4 | Transmission

UDP (BACnet/IP), TCP (BACnet/SC)

TCP

TCP

dielectric layer

3 | Network

BACnet network layer

IP, ARP, RARP

IP

2 | Data link

ISO 8802 (IEEE 802.3)

1 | Physics

Shielded or unshielded single twisted pair (IEEE 802.3cg)

What are the changes in the new 10BASE-T1L standard?
Figure 1. Example of Architecture Using Traditional Field Instruments and Field Instruments Supporting 10BASE-T1L

10BASE-T1L supports two amplitude modes: 2.4 V for cable lengths up to 1000 m and 1 V for cable lengths up to 200 m. By using a peak-to-peak amplitude mode of 1.0 V, the technology can also be used in explosion-proof environments (hazardous areas) and meet the strict maximum energy consumption requirements of explosion-proof environments.

The Advanced Physical Layer (APL) is built on the 10BASE-T1L standard, as defined by the industry consortium, while defining intrinsically safe operation for process automation.

Likewise, Ethernet-APL supports the transition to seamless process automation equipment using field-to-cloud connectivity, including in areas with potentially explosive gas atmospheres in the food and beverage, pharmaceutical, and oil and gas industries. In addition, APL defines the power supply levels to be transmitted over a single twisted pair line.

10BASE-T1L does not define a specific transmission medium (cable). Only return loss and insertion loss requirements for cables are specified. Fieldbus Type A cable is optional. This allows reuse of existing PROFIBUS or FOUNDATION fieldbus wiring. 10BASE-T1L can be used with a pair of balanced conductors over cable lengths up to 1000 m without any problems. However, in noisy industrial environments, shielded cables (such as Type A cables) are required, along with connectors, screw terminals, or punch-down blocks. Some 10BASE-T1L switch chips have integrated diagnostics that check cable signal quality. Therefore, 10BASE-T1L is a very reliable communication technology, even if the wires are mixed together without problems.

What are the advantages of 10BASE-T1L?

Traditional 4 mA to 20 mA with HART®And fieldbus devices have limited data bandwidth, only a few kbps. With 10BASET1L, a transmission speed of 10 Mbps can be achieved. In this way, not only process values ​​but also other device parameters such as configuration and parameterization information can be transmitted. In the future, increasingly complex sensor software updates, as well as fault and network diagnostics (such as short-circuits in sensor lines), can be performed relatively quickly. Configuration is also simpler because 10BASE-T1L eliminates the need for gateways and converters. By eliminating gateways, the cost and complexity of these legacy devices can be greatly reduced, and the data silos created by these devices can be cleaned up.

In addition, more power can be transmitted over the data line. For example: 500 mW can be transmitted in intrinsically safe areas (hazardous areas) and even up to 60 W in non-intrinsically safe areas.

Ethernet standards such as PROFINET, EtherNet/IP, HART-IP, OPC UA or Modbus-TCP and IoT protocols such as MQTT enable simple and powerful connections from field devices to the cloud.

Can 10BASE-T1L be used with switch modules?

As with standard Ethernet, when using 10BASE-T1L, there are bridges that support various network segments and device coupling. Different network topologies can be implemented and used to power connected devices. In process automation, switches are often connected to controllers, HMIs and the cloud. Switches allow media redundancy in the form of a ring topology for increased availability.

In the field of process automation, connections to devices, sensors and actuators are also referred to as spurs, while connections between switches and to control systems are referred to as trunks.

The increasing density of device integration also enables other possibilities. For example: a 10BASE-T1L switch can be integrated into a sensor, which can be directly connected to other sensors that are also powered by the switch. Figure 2 shows an example of the interconnection of different switches.

What are the changes in the new 10BASE-T1L standard?
Figure 2. Example diagram of switch interconnection

Communication with 10BASE-T1L capable devices can be achieved through the host processor. Integrated MAC functionality, passive media converters, or switches with 10BASE-T1L ports are often required.

Table 2 Overview of different communication technologies in process automation

4 mA to 20 mA with HART

Fieldbus

10BASE-T1L

data bandwidth

1.2 kbps

31.25 kbps

10Mbps

Connect to higher-level Ethernet networks

complex gateway

complex gateway

Seamless connection, no gateway

Meter power supply

limited

Intrinsically Safe: 500 mW; Non-Intrinsically Safe:
Up to 60 W (depending on cable)

Professional skills/expertise

Less professional skills/expertise required

Less professional skills/expertise required

University graduates are very familiar with
Ethernet

Can I power the device with “two wires”?

The 10BASE-T1L standard not only provides data communication functions for sensors and actuators, but also provides power supply through signal lines. Specifically, 10BASE-T1L can deliver up to 60 W in non-intrinsically safe areas. In explosion-proof (intrinsically safe) areas, the power is limited to 500 mW; in this case, the signal amplitude is also reduced from 2.4 V for standard applications to 1 V to comply with the strict requirements for the maximum energy applicable to the area. However, in intrinsically safe areas, the transmission distance can only be shortened.

Table 3 summarizes the possible power transfer levels for Type 18 AWG cables at different line lengths and regions.

Table 3 Overview of power transfer levels for different cable lengths (Type 18 AWG)

55V

24V

1000 m

7.7W

1.23W

400 m

20W

3.2W

150 m

52W

8.3W

in conclusion

10BASE-T1L provides a relatively reliable communication standard for process automation with many advantages over traditional 4 mA to 20 mA applications, including the possibility to reuse existing infrastructure.

About the Author

Thomas Brand joined Analog Devices in Munich, Germany, in 2015 while he was still studying for a master’s degree. After graduation, he participated in ADI’s trainee program. In 2017, he became a Field Applications Engineer. Thomas supports large industrial customers in Central Europe with a focus on Industrial Ethernet. He graduated in electrical engineering from the Union University of Education in Mosbach, Germany, and then obtained a master’s degree in international sales from the University of Applied Sciences Konstanz, Germany. Contact information: [email protected]

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