PROFINET IO IRT (Isochronous Real Time) is a type of clocked communication that is optimized for maximum performance. It is often used for motion control applications.
This PROFINET IO communication class is currently available only for Hilscher CIFX with FW > 3.1.x.x (in the CODESYS setup: ../GatewayPLC/HilscherCIFX/Firmware/cifxpnm.nxf).
In order to send clocked I/O data from the application, the interrupt-triggered bus cycle is necessary (for synchronization between the I/O application and the CIFX hardware). This is currently possible only with RTE Vx >= V3.5 SP9, as well as Linux and Hilscher kernel module.
Specific steps should be noted during configuration:
The IRT communication is activated by setting the RT class of a PROFINET IO slave to RTC 3.
For all IRT devices (IRT domains), the network topology (that is, the connectivity of the Ethernet ports) must be recognized internally. This setting is performed in the Topology tab of the PROFINET IO master.
In addition, the cable length between the devices must be defined. A default value of 100m is specified. This setting is performed in the Options tabs of the PROFINET IO device.
A mixed operation between RT and IRT is possible. However, the IRT domains must not be interrupted by RT devices or non-IRT capable switches. This means that the IRT devices at the controller follow immediately after the RT devices.
In order to send the clocked I/O data from the application, the bus cycle task must be set to External and the interrupt mode must be activated in the CFG file ([CmpHilscherCIFX] InterruptMode=1).
See also
