Technical data

Communication
9.4 Communication via PROFINET IO
Function Manual
662 Function Manual, 06/2012, 6SL3097-4AB10-0BP4
9.4.3 RT classes for PROFINET IO
PROFINET IO is a scalable realtime communication system based on Ethernet technology.
The scalable approach is expressed with three realtime classes.
RT
RT communication is based on standard Ethernet. The data are transferred via prioritized
Ethernet telegrams. Because standard Ethernet does not support any synchronization
mechanisms, isochronous operation is not possible with PROFINET IO with RT! The real-
time capability is comparable with the present PROFIBUS DP solutions with 12 MBaud, i.e. a
sufficiently large bandwidth portion is available for the parallel transmission of IT services on
the same line.
The real update cycle in which cyclic data are exchanged depends on the bus load, the
devices used and the quantity framework of the I/O data. The update cycle is a multiple of
the send cycle.
IRT
Two options are available with this RT class:
● IRT "high flexibility"
● IRT "high performance".
Software preconditions for configuring IRT:
● STEP 7 5.4 SP4 (HW Config)
Note
For further information about configuring the PROFINET interface for the I/O controller
and I/O device, please refer to the following document: SIMOTION SCOUT
Communication System Manual.
IRT "high flexibility"
The telegrams are sent cyclically in a deterministic cycle (Isochronous Real Time). The
telegrams are exchanged in a bandwidth reserved by the hardware. One IRT time interval
and one standard Ethernet time interval are created for each cycle.
Note
IRT "high flexibility" cannot be used for isochronous applications.