Glossary · Industrial communication
PROFINET IRT
Also known as: Isochronous real-time, PROFINET isochronous real-time
German: PROFINET IRT
In industrial communication, PROFINET IRT (isochronous real-time) is the PROFINET communication class that reserves time slots in each cycle for real-time frames and synchronizes the devices, using IRT-capable switches in the devices. It supports short cycle times with very low jitter for motion control.
- Industrial communication
- Standards
In one sentence
PROFINET IRT reserves time slots and synchronizes devices, giving short cycles with very low jitter for motion control.
Example
A press line synchronizes its servo drives with PROFINET IRT at a 1 ms cycle so that all axes take their new setpoints at the same moment.
How it applies
- Engineering: IRT requires IRT-capable hardware in all devices and switches on the path. The engineering tool calculates a schedule from the planned topology, so the topology must be configured and match the real cabling.
- Commissioning: Wrong port connections break the schedule. Topology comparison in the engineering tool shows mismatches.
- Operation: Standard traffic (RT and IT) continues in the unreserved part of each cycle.
- Documentation: The documentation team states whether a device supports IRT (conformance class CC-C), the minimum cycle time, and the topology requirements, and explains that replacement devices must be connected to the same ports.
PROFINET IRT vs. PROFINET RT
RT uses prioritized Ethernet frames on standard switches and suits most I/O applications. IRT adds scheduled time slots and clock synchronization, which gives lower Jitter and allows isochronous applications such as coordinated motion.