Bus Communication

The PROFINET communication is realized using 100 MBit/s transfer rate. Real-time frames contain in addition to the process data (36 … 1440 bytes) also an overhead of 44 bytes (gap, preamble and FCS included). The result is a frame length of 80 - 1484 bytes, that means a frame time of 6.4 µs up to 116.4 µs.

The devices CI50x-PNIO are the IO devices for PROFINET RT. The difference of those devices can be found in their input and output characteristics Comparison: Comparison of the CIxyz-PNIO Modules

• The PROFINET IO RT devices CI501-PNIO, CI502-PNIO and CI504-PNIO have a process data length of 80 bytes up to 213 bytes, depending on the usage of expansion modules. That results in a frame time of 6.4 µs up to 17.0 µs for 1 IO device.
• The PROFINET IO RT device CI506-PNIO has a process data length of 80 bytes up to 1024 bytes, depending on the usage of expansion modules. That results in a frame time of 6.4 µs up to 81.7 µs for 1 IO device.

To get the best performance for the PROFINET RT channel a few factors have to be taken into account. These parameters can be set in the configuration tool and define the frequency and distribution of the RT frames.

• SendClockFactor
• ReductionRatio