empowering communication

PROFINET IRT: When Real-Time is not enough

Why do I need PROFINET IRT?

Industrial communication protocols such as PROFINET, EtherCAT and Ethernet/IP are classified as real-time communication protocols. These protocols can already achieve cycle times as low as 1 millisecond and jitter between 10 and 100 microseconds.

In some cases, however, even this level of performance isn’t enough. The fact of the matter is: it takes time to transmit and process data. In certain applications, it is critical that this time be precisely synchronized to ensure that production steps are performed correctly.

This is particularly true in motion control, where the demands for speed and performance in data communication have increased to the point where the cycle times of standard real-time PROFINET are no longer fast enough, and other key metrics such as jitter and determinism no longer meet the required standards.

For example, a robotic arm must be in a precisely defined position at a specific time to pick up or process a part. If the arm is even slightly early or late, the process can be severely disrupted. In such cases, the transmission and processing of data must be both fast and reliable.

PROFINET IRT is used wherever standard real-time communication reaches its limits and extremely accurate synchronization at exceptionally high speeds in data communication are required.

The inside of a factory with a conveyor belt and grey boxes. On the right side is the PROFINET logo.
How Does PROFINET IRT Work?

PROFINET IRT requires strict determinism in the transmission of specific data packets within the network. This means that data must be received, processed, and forwarded in a precise sequence within a predetermined time frame, without being affected by delays such as network collisions or jitter.

To do this, a PROFINET IRT network allocates specific time slots for handling time-critical data. For instance, if 20% of the network traffic is reserved for IRT communication, i.e., PROFINET IRT, the network traffic is divided into five time segments:

  • One segment is dedicated to IRT communication
  • The remaining four segments are reserved for regular real-time communication

In this case, the network operates as a standard PROFINET network 80% of the time. During the remaining 20%, only PROFINET IRT-relevant data packets are processed, ensuring synchronized and deterministic transmission. While IRT communication is taking place, regular PROFINET data packets are buffered and processed when the IRT time segment is complete.

A picture with numerous columns lined up in it. Every fifth column is labeled IRT, while the rest is labeled RT.
For this system to work effectively, a PROFINET IRT network must meet two essential requirements:
Synchronization across all IRT devices

A consistent synchronization cycle must be maintained across all PROFINET IRT devices. This is managed by a high-precision clock that is shared by all devices. This and additional mechanisms such as the Precision Time Protocol (PTP) are defined in the IEEE 1588 standard. PROFINET IRT extends this standard with the Precision Transparent Clock Protocol (PTCP). PTCP not only maintains a shared clock between PROFINET IRT devices, but also calculates delays between network switches and the associated wiring.

An icon of acomputer display with a loading icon in the middle.
Buffering capabilities

Additional circuitry within the network switch is required to buffer any non-IRT Ethernet traffic received during the designated IRT communication time.

PROFINET IRT with Hilscher & netX

In order to meet the requirements of such time-critical data communication, it is necessary to intervene on layer 1 and layer 2 of the OSI model, in particular on the MAC layer. This is necessary so that the network devices can provide the IRT time segments during which the Ethernet communication is converted to a TDMA (Time Division Multiple Access) medium. The rest of the time, during regular PROFINET communication, the data transmission works as a standard CSMA-CD (Carrier Sense Multiple Access - Collision Detect) medium.

Hilscher is one of the few suppliers worldwide to offer PROFINET IRT for controller applications. This is made possible by Hilscher’s netX communication controllers, which are developed together with the corresponding protocol software.

Transport LayerSession LayerPresentation LayerApplication LayerNetwork LayerDataLink LayerPhysical LayerModified Ethernethardware-based RTEHTTP, SNMP, SMTP, FTP, LDAP and similarIE Protocols likePROFINET, EtherCAT, ...Specific Real-Timehardware and functions(for example PROFINETIRT, Sercos, EtherCAT,Powerlink or TSN)Ethernet PHYTransport LayerSession LayerPresentation LayerApplication LayerNetwork LayerDataLink LayerPhysical LayerLegacy FieldbusStandard Ethernethardware-based RTEIP-Multicast IPEthernet MACEthernet PHYHTTP, SNMP, SMTP, FTP, LDAP and similarIE Protocols likePROFINET RT, EtherNet/IP(CIP), Modbus, ...UDPTCP

netX enables PROFINET IRT

Hilscher addresses this challenge with its netX technology. The netX controllers feature a unique xC structure on OSI layers 1 and 2. Using these programmable microcontrollers and Hilscher’s PROFINET protocol stack, the behavior of a PROFINET network can be defined on the first two OSI layers.

A graphical representation of the netX Basic technology switch architecture 100Mbit.

Flexible microcode from Hilscher

A key feature of netX is that this behavior isn’t hardcoded, but can be flexibly adjusted via microcode. With the microcode provided by Hilscher, users have access to the interface between layer 2 and layer 3.

A graphical representation of the netX Basic technology switch architecture 100Mbit.

If you already have a PROFINET solution in place, the first step is to check whether your hardware is IRT-capable. In most cases, it is not, as both hardware and software must meet specific requirements to transmit data according to the IRT standard. These requirements go beyond what is needed for most industrial applications and are typically only needed in high-performance systems, such as those used in motion control or robotics. Unfortunately, many PROFINET-enabled devices are not compatible with PROFINET IRT. In the worst case, a PROFINET IRT network will have to be treated and developed completely separate from your existing installations.

PROFINET and PROFINET IRT with netX

netX technology makes the transition much easier. The necessary PROFINET IRT configurations are already integrated in our standard PROFINET stack, and every netX communication controller comes with the required xC structure. You don’t need to make any changes to either your hardware or software. All you need to do is configure your network.

The same also applies to other network technologies such as EtherCAT. Thanks to the multiprotocol capability of netX, the same hardware can also support EtherCAT.

 

A black square with netX written on it on colorful background. On the right side is a PROFINET logo.

Different cable lengths introduce additional jitter, a physical property that is unavoidable and requires special attention when implementing a PROFINET IRT network.

For example, a data packet sent over a 10-cm cable will have a shorter transmission time than one sent over a 100-meter cable. These different cable lengths and the resulting jitter during data packet transmission must be taken into account in a PROFINET IRT network to ensure that the controller can properly manage the devices on the network.

Hilscher provides a handy tool called the Topology Editor that allows users to map their plant layout and account for the cable lengths connecting their devices.

What devices are suitable for PROFINET IRT?

Devices that meet the requirements for PROFINET IRT are classified as Conformance Class C (CC-C) as part of the PROFINET certification process. This class covers clocked communication with cycle times as low as 32.5 microseconds. CC-C is the most advanced and demanding conformance class for PROFINET. There are other conformance classes as well: CC-A, the basic class, supports “normal” real-time communication, acyclic real-time transmission, and standard TCP-IP Ethernet. CC-B builds on CC-A by adding support for the Simple Network Management (SNMP) protocol. The classes are cumulative, i.e., CC-C not only supports IRT communication, but also includes all features of CC-A and CC-B.

Hilscher’s netX technology is fully compliant with Conformance Class C, as our PROFINET stack already includes all necessary software functions. On the hardware side, our netX communication controllers are also equipped for IRT applications as standard.

PROFINET conformity classABC
Real-time data exchange with cycle times of up to 1 ms
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Alarm and diagnostic functions
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Support for network topology
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SNMP support 
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Real-time data exchange with cycle times down to 31.25µs  
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Our PROFINET PC cards

PC card PCI Express - Real-Time Ethernet

Communication for PC-based automation

PC card for extended temperature range PCI Express - Real-Time Ethernet

Communication for PC-based automation

PC card Mini PCI Express halfsize - Real-Time Ethernet

Communication for PC-based automation

Detached network interface Real-Time Ethernet

Communication for PC-based automation

Detached network interface Real-Time Ethernet

Communication for PC-based automation

PC card M.2 2230 Key A+E - Real-Time Ethernet

Communication for PC-based automation

PC card M.2 3042 Key B+M - Real-Time Ethernet

Communication for PC-based automation

Detached network interface Real-Time Ethernet

Communication for PC-based automation

Detached network interface Real-Time Ethernet with M12 connectors

Communication for PC-based automation

PC card M.2 2242 Key B+M - Real-Time Ethernet

Communication for PC-based automation

PC card low-profile PCI Express - Real-Time Ethernet

Communication for PC-based automation

PC card with NVRAM low-profile PCI Express - Real-Time Ethernet

Communication for PC-based automation

PC card with NVRAM Mini PCI Express - Real-Time Ethernet

Communication for PC-based automation

PC card Mini PCI Express - Real-Time Ethernet

Communication for PC-based automation

Detached network interface Real-Time Ethernet

Communication for PC-based automation

Detached network interface Real-Time Ethernet with M12 connectors

Communication for PC-based automation

PC card with NVRAM and extended temperature range Mini PCI Express - Real-Time Ethernet

Communication for PC-based automation

PC card without heat sink Mini PCI Express - Real-Time Ethernet

Communication for PC-based automation

PC card for extended temperature range Mini PCI Express - Real-Time Ethernet

Communication for PC-based automation

PC card PCI - Real-Time Ethernet

Communication for PC-based automation

PC card CompactPCI - Real-Time Ethernet

Communication for PC-based automation

PC card Mini PCI - Real-Time Ethernet

Communication for PC-based automation

Detached network interface Real-Time Ethernet

Communication for PC-based automation

Detached network interface Real-Time Ethernet with M12 connectors

Communication for PC-based automation

Our embedded modules for PROFINET

Communication module dual-port memory - Real-Time Ethernet

Flexible communication module for automation

Communication module SPI - Real-Time Ethernet Slave

Flexible communication module for automation

Communication module dual-port memory - Real-Time-Ethernet

Flexible communication module for automation

Communication module SPI - Real-Time Ethernet Slave

Flexible communication module for automation

comX Evaluation Board

Development platform for all comX types

netX 90 Chip Carrier - preloaded protocol stack

Ultracompact netX 90 design - tested and loaded completely

netX 90 Chip Carrier with an additional memory - preloaded protocol stack

Ultracompact netX 90 design - tested and preloaded completely

netRAPID H90 Evaluation Board - Real-Time Ethernet & Fieldbus

Equipped with an NRP H90-RE\F8D8

netX 51 Chip Carrier with an additional memory - Real-Time Ethernet slave

Ready-to-solder netX design in stamp format

netRAPID 51 Evaluation Board - Real-Time Ethernet

Equipped with an NRP 51-RE

netX 52 Chip Carrier incl. transformer - Real-Time Ethernet slave

Ready-to-solder netX design in stamp format

netRAPID 52 Evaluation Board - Real-Time Ethernet

 

Exchangeable Module PCI Express - Real-Time Ethernet

For mounting at any time in the delivery chain

Exchangeable module SPI - Real-Time Ethernet Slave

For mounting at any time in the delivery chain

Exchangeable module dual-port memory - Real-Time Ethernet

For mounting at any time in the delivery chain

netJACK Evaluation Board dual-port memory

For every netJACK with dual-port memory or SPI

netJACK Evaluation Board PCI Express

For every netJACK with PCI Express

DIL-32 communication IC for fiber optic cable - PROFINET IO-Device

Communication for simple slave devices with connection to fiber optic cable

DIL-32 communication IC without heat sink - Real-Time-Ethernet slave

Communication for simple slave devices without a host processor of their own

DIL-32 communication IC - Real-Time-Ethernet slave

Communication for simple slave devices without a host processor of their own

netIC Evaluation Board with fiber optic cable - PROFINET IO-Device

Evaluation platform netIC with fiber optic cable

DIL-32 communication IC for fiber optic cable - PROFINET IO-Device

Communication for simple slave devices with connection to fiber optic cable

netIC Evaluation Board - Real-Time-Ethernet slave

An evaluation platform for all Real-Time-Ethernet protocols

DIL-32 communication IC - Real-Time-Ethernet slave

Communication for simple slave devices without a host processor of their own

Our gateways for PROFINET

Media Switch SPE to RTE

Connects Single Pair Ethernet networks with Realtime-Ethernet protocols

Gateway CANopen to Ethernet

Cost-optimized entry level gateway for simple conversions

Gateway CC-Link IE Field Slave to PROFINET IO-Device

Data coupling between CC-Link IE Field and PROFINET

Gateway Real-Time Ethernet to DeviceNet

High-end gateway for demanding conversions

Gateway PROFIBUS DP to Ethernet

Cost-optimized entry level gateway for simple conversions

Gateway Real-Time Ethernet to Real-Time Ethernet

Data transmission between two Real-Time Ethernet networks

Gateway Real-Time Ethernet to Modbus RTU, 3964R, or Serial (ASCII / programmable)

High-end gateway for demanding conversions

Gateway DeviceNet to Ethernet

Cost-optimized entry level gateway for simple conversions

PROFINET / PROFIBUS Proxy connector

Upgrading a PROFIBUS Slave to PROFINET

Gateway Serial (ASCII) or Modbus RTU to Ethernet

Cost-optimized entry level gateway for simple conversions

Gateway Real-Time Ethernet to CC-Link Slave

High-end gateway for demanding conversions

Gateway CC-Link Slave to Ethernet

Cost-optimized entry level gateway for simple conversions

Gateway Real-Time Ethernet to Ethernet

High-end gateway for demanding conversions

Gateway Real-Time Ethernet to PROFIBUS DP

High-end gateway for demanding conversions

Gateway Real-Time Ethernet to CANopen

High-end gateway for demanding conversions

Ethernet LAN PROFINET IO-Controller

LAN-controlled PROFINET IO-Controller for the DIN rail

Ethernet LAN Real-Time Ethernet multiprotocol

LAN-controlled Real-Time Ethernet Master for the DIN rail

Gateway PROFINET IO-Device to SmartWire-DT

SmartWire-DT connectivity to Real-Time Ethernet PROFINET systems

Related links
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From turn-key products to highly integrated solutions and complementary software, Hilscher is your partner for industrial communication. Get an overview of how we can help you take the networking of your machines to a whole new level!

Communication controllers and printed circuit boards are extensively tested at Hilscher in Germany.

We make industrial communication possible. From legacy fieldbus to Real-Time Ethernet and the cloud. Our solutions are multi-protocol capable, flexible and reliable. Learn more about how our netX software and hardware technologies work and how we make machine data accessible for you with our IIoT platform netFIELD.

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Customer Center / Sales: Hilscher North America, Inc.

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