Advanced physical layer
Ethernet Advanced Physical Layer ( Ethernet APL ) describes a physical layer for Ethernet communication technology that was specially developed for the requirements of the process industry. The reason for the development of Ethernet APL was the need for high-speed communication over long distances, the provision of power and communication signals via a single 2-wire cable, and protective measures for safe operation in hazardous areas.
As part of the widely used Ethernet standard, which was specially developed for demanding industrial applications, Ethernet APL offers a high degree of robustness for extremely reliable operation.
In the field of information technology, Ethernet has long since become the standard communication solution. Industrial Ethernet is the common name for the variant of this standard for the manufacturing and process industry . Ethernet APL was developed as the previously missing connection and extends the standardized Ethernet communication up to field instrumentation.
construction
Ethernet APL is one of the possible physical layers of Ethernet, independent of protocols or communication stacks, and is designed for broad acceptance and application in process automation.
| OSI layer (de) | OSI layer (s) | Logs | ||||
|---|---|---|---|---|---|---|
| 7th | application | Application | EtherNet / IP , HART-IP , OPC UA , PROFINET , http ... | |||
| 6th | presentation | Presentation | ||||
| 7th | meeting | session | ||||
| 4th | transport | transport | UDP , TCP | |||
| 3 | network | Network | IP | |||
| 2 | Fuse | Data link | CSMA / CD , RTE , TSN | |||
| 1 | Bit transfer | Physical |
Ethernet Fast Ethernet Gigabit Ethernet WLAN ... |
Ethernet APL | ||
Ethernet as the basis for APL
Ethernet APL is a special 2-wire Ethernet based on 10BASE-T1L according to IEEE 802.3cg with additional precautions for the process industry. The Ethernet APL communication is therefore part and fully compatible with the IEEE 802.3 Ethernet specification.
The transmission takes place with a data transmission rate of 10 Mbit / s, is coded 4B3T and modulated as PAM-3 and transmitted with 7.5 M baud full duplex .
The structure can consist of a " trunk " cable with a maximum of 1000 m between the field switches in zone 1 and the "track" cable with a maximum of 200 m in zone 0 between a field switch and a field device.
Ethernet APL contains a number of extensions that are specially tailored to the demanding requirements of the process industry and other sectors, such as intrinsic safety and port profiles for optional power supply to the connections.
Intrinsic safety
Intrinsic safety is an essential requirement of the global process industry , which demands an easy-to-implement solution for the control and power supply of field devices in hazardous areas. Intrinsic safety is fully integrated into the Ethernet APL as an option.
The intrinsically safe 2-wire Ethernet is to be defined in the technical specification IEC TS 60079-47 ED1.
The intrinsic safety barrier is an electronic circuit at each output or input of a distributor / switch or field device. This prevents ignitable electrical energy from reaching the connection. The intrinsic safety barrier is separated from the communication circuit (PHY), which is a simple but important part of the Ethernet APL design. This construction principle ensures:
- Chip manufacturers can produce PHY chips in quantities that can be used in applications that do not require intrinsic safety
- Device manufacturers can easily build intrinsically safe devices
Ethernet APL supports the simple planning, validation, installation, documentation and implementation of the intrinsically safe operation of field devices in potentially explosive areas. This includes working on cables and instruments without a certificate of authorization. All suitable products must be approved by a notified body .
Port profiles
The standards for Ethernet APL include the definition of port profiles for the connections for interoperability in various application scenarios. This includes aspects such as the segment type, which distinguishes a trunk-to-trunk port from a track-to-track port. Other specifications relate to the characteristics of the power supply and distinguish e.g. B. Connections between power source and sink or connections without power supply. Another chapter contains the definition of power classes for energy supply. This includes the limitation of the maximum supply voltage and the supply current for an intrinsically safe power supply.
Other topics of Port Profile specification, wiring rules, pin assignments for terminals and connectors and Schirmauflage- and ground rules .
Further information
- Benedikt Spielmann: Ethernet to the Field of Process Plants / Sites , presentation at the ODVA conference on March 4, 2020 (English) https://www.odva.org/Portals/0/Library/Conference/2020-ODVA-Conference_Ethernet- APL_Spielmann_Final_PPT.pdf
Individual evidence
- ↑ IEEE Standards Association: 802.3cg-2019 - IEEE Standard for Ethernet - Amendment 5: Physical Layer Specifications and Management Parameters for 10 Mb / s Operation and Associated Power Delivery over a Single Balanced Pair of Conductors available at https://standards.ieee .org / standard / 802_3cg-2019.html
- ↑ Advanced Physical Layer APL. In: PI White Paper. Profinet International, 2018, accessed October 9, 2019 .
- ↑ a b International Electrotechnical Commission: IEC TS 60079-47 ED1: Equipment protection by 2-Wire Intrinsically Safe Ethernet concept (2-WISE) is to be published in 2020.
- ↑ Example of the professional association for wood and metal: Permission for work with risk of ignition , form available at https://www.bghm.de/fileadmin/user_upload/Arbeitsschuetzer/Praxishilfen/Formulare/Brand_und_Explosionsschutz/Erlaubnis_fuer_Arbeiten_mit_Zuendgefahr.doc