General Purpose Single Pair Ethernet
for Process Instruments
David D. Brandt
Engineering Fellow
Rockwell Automation, Inc.
Michael Bückel
Head of Department | MTMP Platforms
Endress+Hauser Flowtec AG
Presented at the ODVA
2023 Industry Conference & 22nd Annual Meeting
October 18, 2023
El Vendrell, Spain
Abstract
ODVA has demonstrated industry leadership in Single Pair Ethernet (SPE) solutions. External promotion
included liaison with IEEE P802.3cg project, and active stakeholder position in the APL Project. Domainspecific specification EtherNet/IP enhancements include an “In-cabinet” SPE solution (motor control
components), and “Ethernet-APL” (process instruments for hazardous locations). Further specification
enhancements are underway in the EtherNet/IP Physical Layer Special Interest Group for “GPSPE”(general purpose SPE). One intent of GPSPE is to utilize 10BASE-T1L to extend SPE use cases - byreaching out from inside the cabinet and into non-hazardous field locations. Another intent of GPSPE is toreference existing/emerging SPE standards rather than invent new technology. GPSPE will be useful toexpand the application space of EtherNet/IP for constrained devices across industrial domains (discrete,
hybrid, and process automation) – reducing the end-device electronics and field cabling. This paper
discusses use cases and benefits when utilizing GPSPE with new Process Instruments. This paper also
discusses minor changes that allow – EtherNet/IP end-devices using Ethernet-APL to interoperate withother GPSPE devices.
Keywords
Ethernet, IEEE 802.3, IEEE 802.3cg, SPE, Industrial Automation, Process Automation, In-cabinet,
Ethernet-APL, Fieldbus, Intrinsic Safety, ODVA, EtherNet/IP, GPSPE
Definition of terms
Industrial Automation
Ethernet
Industrial Ethernet
Fieldbus
SPE
IEEE 802.3cg
EMC
MAC

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Discrete, Process, and Hybrid (Batch) Automation
IEEE 802.3 standards, including MAC and PHY definitions
Ethernet infrastructure suited for industrial automation
Industrial networks for real-time control (not Industrial Ethernet)
Single Pair Ethernet
SPE including 10BASE-T1L and 10BASE-T1S PHYs
Electro-Magnetic Compatibility
Medium Access Control layer (IEEE)
1©2023 ODVA, Inc.

PHY
GPSPE
ESE
Edge
Gateway
SwitchHazardous location
Intrinsic safety
HART
CAN
Ethernet-APL
PoDL
PSE
PD

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PHYsical layer connecting a link layer to a physical medium
General Purpose Single Pair Ethernet, proposed ODVA specification
EtherNet/IP Specification Enhancement
Leaf nodes attached to a network core, i.e., sensor and actuators
Network protocol converter spanning ISO model layers
IEEE 802.3 bridge, forwarding based on MAC addresses
Area that may have an explosive atmosphereTechnique for safe operation in hazardous locations
Link protocol, Highway Addressable Remote Transducer
Communication protocol, Controller Area Network
Advanced (Ethernet) Physical Layer for Process Automation
Power over Data Lines, IEEE standard for powering an SPE pairPower Sourcing Equipment - power supply for a PoDL PD
Powered Device – load for a PoDL PSE

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Evolution of Industrial Ethernet
Industrial Ethernet solutions emerged rapidly in the decade from 2000-2010. As shown in Figure 1, highgrowth led to the steady displacement of many fieldbus and sensor networks, however, complete
transition has been hindered by cost and features [3].

Figure 1: Industrial Ethernet and Fieldbus market share over time.

Pursuing higher performance, much of Industrial Ethernet is in transition from 10 and 100 Mb/s over twopairs to 1 Gb/s over four-pairs. While the cabling cost increases, there are also substantial cost, size, andpower increases in the magnetic coupling circuits, EMC protection circuits, and PHY packaging.
Application to small devices (often hardwired) is then limited.
Additionally, multipair Industrial Ethernet is limited in distance to 100 m, does not power the sensor, andis not directly compatible with hazardous environments. Therefore, multipair wiring is generally notaccepted in the field networks and limited in its application to Process Automation use cases.
The multipair Industrial Ethernet limitations and direction make it increasingly difficult to displace somefieldbus and sensor networks, and to achieve the transition from hardwired devices to networked devices.
The result is a network with non-homogenous communication, a variety of technologies that are notfamiliar to most graduates, limited data flow, and lack of end-to-end security. Therefore, engineering andoperations face additional costs and efforts for commissioning and maintenance of this mix oftechnologies.
SPE has emerged as a potential response to displace the remaining fieldbuses, sensor networks, andsome hardwired solutions at the edge of the network.
Automotive pioneered SPE when they realized that the wiring harness had become the third heaviest
component in the car. They also realized that the number of types of networks in the car (overlapping
cables in the wiring harness) was continuing to expand. A further realization was that useful information
was trapped in these separate systems. (An example is that the wheel speed sensor could be used with
the GPS system to track location in a dark tunnel and turn headlights on and off on entry and exit.)
Secure networking has become another requirement.
The automotive industry began to aggressively pursue an all-Ethernet vehicle. SPE solutions werestandardized within IEEE to cover a range of speeds from 100 Mb/s to greater than 10 Gb/s.
The automotive vision was compelling and led industrial automation organizations to become engaged inIEEE to develop SPE that was suited to industrial scale and needs. The result was IEEE Std 802.3cg2019. There were two new SPE PHYs introduced in that standard. 10BASE-T1L is used in Ethernet-APL
to meet requirements for long distances and for intrinsically safe implementation. 10BASE-T1S was
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driven by both automotive (primary) and industrial to achieve a lowest cost solution for Ethernet. Like with
CAN in DeviceNet, industrial can leverage automotive SPE volumes.
Beyond the IEEE standard, there has been standardization of cables and connectors. There is also ongoing standardization within industrial organizations – including ODVA. Multiple silicon vendors haveintroduced PHYs. Devices are in development and poised to emerge.
Published ODVA Specifications Leveraging SPE
ODVA has demonstrated industry leadership in Single Pair Ethernet (SPE) solutions. External promotion
included liaison with IEEE P802.3cg project, and active stakeholder position in the APL Project.
One ODVA domain-specific SPE solution is an EtherNet/IP specification for cabinets containing motor
control components. This is depicted in Figure 2. The specification is included in Chapter 8-10 “Industrial
EtherNet/IP In-cabinet Bus Media and Physical Layer”.

Figure 2: SPE domain and challenges for In-cabinet solution.

Another ODVA domain-specific SPE solution is an EtherNet/IP specification for process instruments forhazardous locations. This is depicted in Figure 3. The specification is included in Chapter 8-11
“EtherNet/IP Media and Physical Layer for Ethernet-APL (Ethernet Advanced Physical Layer)”

Figure 3: SPE domain and challenges for process automation solution.

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ODVA General Purpose SPE (GPSPE) Initiative
The EtherNet/IP Physical Layer Special Interest Group is developing EtherNet/IP Specification
Enhancements (ESEs) for General Purpose SPE (GPSPE). One reason to call it “general purpose” is theintent of GPSPE to reference emerging standards, including IEEE Std 802.3-2022 (as amended by IEEE
Std 802.3cg-2019), ISO/IEC 11801-3 AM1, ANSI/TIA 568.7A, and IEC 63171 - rather than invent newtechnology. The current effort is to reference 10BASE-T1L.
One intent of GPSPE is to extend the SPE application space of EtherNet/IP for constrained devices
across industrial domains (discrete, hybrid, and process automation) – reducing the end-device
electronics and field cabling.
One GPSPE use case is to reach out from the control cabinet and into non-hazardous field locations. Thisis depicted in Figure 4 for discrete automation. Note that Ethernet-APL can reach out from a cabinet andinto the field – for hazardous locations.

Figure 4: GPSPE non-hazardous domain – reaching from cabinets into the field.

Since GPSPE is an on-going effort, many decisions have not been made or are subject to change.
Relation of GPSPE to EtherNet/IP for Constrained Devices
EtherNet/IP for constrained devices includes both:• Reduced physical layero Cablingo Connectors
o Coupling circuito EMC protectiono SPI MAC/PHY interface• Reduced protocol stacko Less FLASH and RAM for smaller MCUso Transport (UDP-only)
o Security (DTLS-only)
GPSPE specifies a reduced physical layer. Devices can also implement the reduced protocol stack.

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GPSPE Use Cases for Process Instruments
Non-hazardous instrument applications include many Process Skids (e.g., as shown in Figure 5). Theseskids are often specialty OEM modules that are shipped and placed at an end site. The skids may beinterconnected via piping and supervisory communication to perform a series of production functions. The
distances are short. These OEM applications are cost sensitive.

Figure 5: Many Process Skids utilize instruments in non-hazardous locations.

Other non-hazardous instrument applications are included in the plantwide automation for Life Sciences,
Food and Beverage, and Water and Wastewater industries, as depicted in Figure 6 These industries may
utilize skids as elements a larger plant. The distances are larger than on skids, but smaller than with large
plants like in Oil and Gas.

Figure 6: Industries where instruments are prevalent in non-hazardous locations.

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The introduction of SPE (Ethernet-APL) is driving all instruments toward Ethernet connection inhazardous areas. Harmonization on a full suite (see Figure 7) of EtherNet/IP instruments has numerous
advantages:• Fast updates• Reduction of gateways• Reduction of cabling – single pair with power• Increased information capability from some instruments• Ability to have multiple measurements from the same instrument.

Figure 7: Instrument types.

Non-hazardous locations do not yet have a full suite of SPE-based EtherNet/IP instruments. A limited set
of EtherNet/IP instruments is sometimes utilized. These instruments are typically supplemented with
HART instruments when no equivalent EtherNet/IP instrument is available.
GPSPE could drive all instrument types toward Ethernet connection within non-hazardous areas.
GPSPE Power Classes
GPSPE will reference IEEE Std 802.3-2022 Clause 104 (PoDL) for power options.
The PSE and PD are Type E, allowing longer distances.
Classes 10-15 will be used (see Figure 8). These were added within IEEE for long reach (1000 m) andindustrial usage. Classes 0-9 exist primarily for short reach (15 m) and automotive usage.
Both Plug and Play and Engineered power are being considered.

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Figure 8: GPSPE Power Classes.

Comparison of GPSPE with Ethernet-APL for Process Instruments
GPSPE shares basic Ethernet technology with Ethernet-APL, but each has optimizations for different
industry segments. Table 1 compares multiple aspects of GPSPE and Ethernet-APL. Both support
EtherNet/IP communication over 10BASE-T1L. Differences primarily relate to the Ethernet-APL
requirement to operate in hazardous locations. This leads to intrinsic safety requirements, which lead to acustom engineered power solution.
Table 1: GPSPE Comparison to Ethernet-APL for Process Instruments.

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Intrinsic Safety Comparison of GPSPE with Ethernet-APL
Ethernet-APL devices and switches are specified for hazardous locations as found in Oil andGas, and Chemical industries. The inclusion of intrinsic safety in Ethernet-APL devices
requires a level of redundant hardware for protection against faults that can cause hazardous
conditions. The amount of hardware increases with higher power levels. Switches supply
power for multiple devices and have larger overhead.
GPSPE will be specified for non-hazardous locations. This reduces the redundant hardware andeliminates a major certification process. As a result, the GPSPE field device and switches are expected tobe more cost efficient than the Ethernet-APL field devices and switches.
Ethernet-APL power and voltage are quite limited due the intrinsic safety requirements. Power Class A(Ex ia IIC) provides 0.5 W @ 15 V to a device. Power Class C provides 1 W @ 15 V to a device, but only
for less hazardous environments (Ex ic IIC).
While these power levels are sufficient for most of the sensor instruments in the field,
there are still specific instruments, such as flow meters, that benefit from more power
and therefore require secondary power supply. The secondary source would itself
need to be compatible with the hazardous location. This could mean a second
identical cable run (also low wattage) that might be run for 200 m. As an alternative,
the power cable may be run in an expensive explosion-proof conduit and extra
measures taken in the device. Already Ethernet-APL is a large step up from 4-20 mA or HART, but thepower budget is still below the optimal level.
On the other hand, GPSPE does not have these power restrictions, as no intrinsic safety requirements
needs to be fulfilled. To power typical process sensors known in the non-hazardous industries, an 8 W
power budget is desirable. In most cases this is sufficient even for demanding flow sensors.
GPSPE is expected to specify PoDL (Power over Data Line) Classes 10,11 and 12. An SPE switch
implementing the PSE (Power Supply Equipment) function would source 30 Vdc and deliver up to 8.4 W
to a PD (Powered Device). The switch itself may operate from and distribute power from a higher
powered GPSPE link or from separate power.
Extension of GPSPE with Ethernet-APL Devices
While the ODVA GPSPE specification is still in development, the specification for EtherNet/IP for
Ethernet-APL has already been published. Vendors are currently preparing Ethernet-APL Field Devices(and switches) for the market.
There are advantages in enabling these Ethernet-APL devices to be able to attach to GPSPE:• Hardware platform and firmware re-use• Faster launch of GPSPE
Other devices might be specifically optimized (i.e., without Intrinsic Safety or utilizing more power) for
GPSPE.
Ethernet-APL and GPSPE devices are potentially interoperable via switching (both are EtherNet/IP over
10BASE-T1L). However, the power systems are different (see Table 1). Subsequent sections discuss thedifferences.
Figure 8 illustrates the concept of an optional “compatibility mode” between Ethernet-APL and GPSPE.
An Ethernet-APL device that supports compatibility mode could operate with either switch.
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Compatibility mode has the following attributes for Ethernet-APL field devices:• Device is able to operate at a higher GPSPE voltage level• Device is not damaged by the increased voltage• Device follows GPSPE connector scheme• Device is labelled properly for non-IS locations
Compatibility mode has the following attributes for GPSPE switches:• Can be configured to apply power directly to Ethernet-APL field devices

Figure 9: GPSPE compatibility mode for Ethernet-APL.

Harmonizing GPSPE and Ethernet-APL PowerThe GPSPE PSE would normally interact with the PD and not turn on full voltage unless a PD is present
on the link. Various interaction methods are possible. The first method is Detection. A low voltage signal
is placed on the link by the PSE and a PD will draw a specified current if present. The PSE must be preconfigured to supply a specific voltage and power (i.e., it is set to a specific Class). A second method isClassification, where information is exchanged between PSE and PD. This also allows PD detection – aswell as the establishment of the Class without pre-configuration.
Unfortunately, unmodified Ethernet-APL devices do not support Detection or Classification. The EthernetAPL Source (power supply to a link) is directly enabled to the Ethernet-APL Load (powered device on alink) – regardless of whether a device is present. The circuitry for PoDL was never specified for intrinsic
safety. Additionally, the PoDL circuitry would potentially cut into the limited Ethernet-APL power budget.

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One simple method for powering Ethernet-APL devices in a GPSPE system is known as PoDL-bypass.
The PSE is pre-configured to provide a full voltage to the link without Detection or Classification.
The PSE Source utilizes PoDL coupling circuit and a subset of the state machines.
PoDL-bypass Considerations - Damage
The pre-configured voltage in PoDL-bypass could be specified as 30 Vdc (Class 10-12)
and/or 58 Vdc (Class 13-15). It is important to prevent damage.
GPSPE is expected to support both PoDL voltages and to retain the IEEE requirement for10BASE-T1L is to tolerate up to 60 Vdc. GPSPE devices could never be damaged by direct
application of 58 Vdc.
Ethernet-APL devices are not required to tolerate 60 Vdc. Ethernet-APL Field Switches Classes A and C
only supply 15 Vdc to the Field Devices. This voltage and the matching current fit under the ignition
curves (limits to not ignite an explosive atmosphere) and were found as optimal in power delivery. Some
vendors have mentioned implementing non-replaceable fusing that would open before even reaching 30
Vdc. Other vendors may not have the fuse problem.
PoDL-bypass Considerations – Voltage Selection
It is proposed that GPSPE only specify a PoDL-bypass option for Classes 10, 11 and 12 (30 Vdc). An
Ethernet-APL device could be powered in a GPSPE system - if it operates from and tolerates 30 Vdc.
Limiting the pre-configuration voltage to 30 Vdc and designing the Ethernet-APL device to operate fromand tolerate this voltage would preclude damage.
Pre-configuration of 58 Vdc may not have an advantage. 8 W is considered adequate. The nonhazardous applications do not require 1000 m distances. Likely 200 m is adequate. Class 12 voltage drop
across a 200 m cable must meet the 9.5 Ω loop resistance. For a 400 m loop, we have 0.024 Ω/m (i.e.,18
AWG wires).
Design for operation/tolerance is considered more difficult. The component ratings are higher incomparison to the 15 Vdc usage, sizes are larger, and heat dissipation is likely a concern.
Additional qualification and installation restrictions may also apply when exceeding 50 V due to potential
shock hazard. This is especially true for wet installations.
PoDL-bypass Considerations – Misapplication
A related issue concerns moving an Ethernet-APL instrument between hazardous and non-hazardous
locations. When the device is placed in the non-hazardous location, there is no guarantee the device will
not sustain hidden faults. When placed back in a hazardous environment, the device may not perform as
intended.
It is required that for Ethernet-APL devices to be used with GPSPE, the devices are packaged andlabelled without hazardous area approval markings. It is also proposed that GPSPE avoid re-use of the
Ethernet-APL specified M8 and M12 connectors. These measures reduce the possibility of misapplicationand still allow the bulk of the hardware and firmware to be re-used.

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Conclusions
GPSPE continues the trend of using SPE to displace fieldbus, sensor, and device networks - and toenable networking of hardwired devices and devices from point-point links.
Non-hazardous process applications are prevalent.
A complete portfolio of EtherNet/IP instruments is desirable for:• Hazardous locations (Ethernet-APL)• Non-hazardous locations (GPSPE)
GPSPE is anticipated to bring advantages to Process Instruments in non-hazardous locations:• Reduced wiring• Lower cost by eliminating Intrinsic Safety• Significant power
While there is advantage in allowing Ethernet-APL instruments to be interoperable with GPSPE - theymust be designed appropriately.
References[1]

2020 ODVA Industry Conference, “Enhancements to Single-pair Ethernet for Constrained
Devices”, March 4, 2020, https://www.odva.org/wp-content/uploads/2020/05/2020-ODVAConference_SPE_Constrained_Malkan_Wang_Brandt_Martin_Final.pdf[2]2018 ODVA Industry Conference, “Enhancements to EtherNet/IP for Constrained Devices andNetworks”, October 10, 2018, https://www.odva.org/wp-content/uploads/2021/09/Paper-11_2018ODVA-Conference_Brandt-XuHahniche_Dietrich_Enhancements_EtherNetIP_Constrained_Devices_FINAL.pdf[3]

2017 ODVA Industry Conference, “IEEE 802.3cg (10SPE) – 10 Mb/s Single Pair Ethernet
meeting Industrial Automation objectives”, February 22, 2017, https://www.odva.org/wpcontent/uploads/2021/09/2017-ODVA-Conference_Brandt-Xu-Haehniche_IEEE-802-3cg10SPE_R0_FINAL.pdf******************************************************************************************************************************************************The ideas, opinions, and recommendations expressed herein are intended to describe concepts of the author(s) for the possible useof ODVA technologies and do not reflect the ideas, opinions, and recommendation of ODVA per se. Because ODVA technologies
may be applied in many diverse situations and in conjunction with products and systems from multiple vendors, the reader andthose responsible for specifying ODVA networks must determine for themselves the suitability and the suitability of ideas, opinions,and recommendations expressed herein for intended use. Copyright ©2023 ODVA, Inc. All rights reserved. For permission to
reproduce excerpts of this material, with appropriate attribution to the author(s), please contact ODVA on: TEL +1 734-975-8840
FAX +1 734-922-0027 EMAIL odva@odva.org WEB www.odva.org. CIP, Common Industrial Protocol, CIP Energy, CIP Motion, CIP
Safety, CIP Sync, CIP Security, CompoNet, ControlNet, DeviceNet, and EtherNet/IP are trademarks of ODVA, Inc. All othertrademarks are property of their respective owners.

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