What are the changes in the new 10BASE-T1L standard?

The New 10BASE-T1L Standard—Has Anything Changed?

What are the changes in the new 10BASE-T1L standard?

summary

Many aspects of our daily lives are inseparable from data communication between various devices. The proliferation of devices and the sharp increase in data volume brought about by digitalization and Industry 4.0 are changing the communication field. For example, fields such as process automation require the use of integrated networks to support factory-wide connectivity needs. We must extract and process data from operational technology (OT) machines, and then provide the processed data to corporate-level computer systems (IT) for further processing. Since previous 4 mA to 20 mA or fieldbus applications have encountered bottlenecks in data communication, Ethernet has begun to become a communication standard. First is the new Ethernet standard 10BASE-T1L, a 2-wire Ethernet solution with a line length of up to 1000 meters and a transmission speed of 10 Mbps, while supporting transmission protocols such as PROFINET, Ethernet/IP, OPC UA, Modbus-TCP, etc. With this standard, we can continue to use existing 2-wire wiring, thereby avoiding wasting our investment.

This article introduces the basics of 10BASE-T1L and shows the products related to selecting the right connector for various applications. Power transmission over data lines to interconnect various devices also plays a vital role in 10BASE-T1L.

Introduction

Data communication plays an increasingly important role not only in the industrial field, but also in the process automation field. The previous 4 mA to 20 mA or fieldbus applications began to encounter bottlenecks due to the surge in 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 is located above the physical layer and is compatible with existing 100 Mbps or 1000 Mbps industrial Ethernet technology, so it can be used as a supplement.

10BASE-T1L is starting to be standardized, especially in the field of process automation, and has the potential to revolutionize this 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, sensors and actuators in process automation are usually located at a distance from the control system or remote I/O system. Distances of 200-1000 meters or more are common.

But what exactly is 10BASE-T1L, what advantages does this technology offer, and why is it becoming the new standard?

We will answer these questions in the following sections.

What does 10BASE-T1L mean?

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

The "10" in the media type refers to a 10 Mbps transmission rate. "BASE" refers to baseband signaling, meaning that only Ethernet signals can be transmitted over the medium. The "T" stands for "twisted pair." The number "1" represents a 1 km range. In this case, the "L" that follows stands for "long reach," meaning the segment length may be 1 km or even longer.

There are also other network technologies 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 (wideband coaxial cable with multiple baseband channels and a maximum segment length of 3600 m).

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

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

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

MAC is defined by the Ethernet standard IEEE 802.3 and is implemented in the data link layer (Layer 2). PHY constitutes 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 be used with it?

10BASE-T1L is designed to replace the 4 mA to 20 mA standardized signal 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-enabled field instruments. These legacy devices can be connected via software-configurable I/O (SWIO) modules, with the remote I/O acting as a collection point connected to the PLC via a 10 Mbps Ethernet uplink.

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

In some cases, the need to power devices as well as transmit device data via 10BASE-T1L is defined as part of the standard. Figure 1 shows an example of a mix of legacy field instruments connected via a 4 mA to 20 mA current loop and newer field instruments that support 10BASE-T1L.

Table 1 Overview of the OSI model and its protocols and bus systems

Figure 1. Example of an 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 the 1.0 V peak-to-peak amplitude mode, the technology can also be used in explosion-proof environments (hazardous areas) and meet the strict maximum energy consumption requirements of explosion-proof environments.

According to an industry consortium, the Advanced Physical Layer (APL) builds on the 10BASE-T1L standard and defines intrinsically safe operation for process automation.

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

10BASE-T1L does not define a specific transmission medium (cable). Only the return loss and insertion loss requirements of the cable are specified. Fieldbus Type A cables are optional. This allows the reuse of existing PROFIBUS or Foundation Fieldbus wiring. 10BASE-T1L can be used with a pair of balanced conductors over cables 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 switches have integrated diagnostics to check the cable signal quality. Therefore, 10BASE-T1L is a very reliable communication technology, even if wires are mixed together.

What are the advantages of 10BASE-T1L?

Conventional 4 mA to 20 mA with HART® and fieldbus devices have a limited data bandwidth of only a few kbps. With 10BASE-T1L, transmission speeds of 10 Mbps can be achieved. This allows not only the process value to be transmitted, but also other device parameters such as configuration and parameterization information. 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 no longer requires the use of gateways and converters. By eliminating gateways, the cost and complexity of these older devices can be greatly reduced, and the data silos created by these devices can be eliminated.

Furthermore, higher powers can be transmitted via the data lines: for example, 500 mW in the intrinsically safe area (hazardous area) and even up to 60 W in the non-intrinsically safe area.

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 a switch module?

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

In process automation, the connections to devices, sensors and actuators are called branches, while the connections between switches and to the control system are called 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.

Figure 2. Example of switch interconnection diagram