The data volume per participant is dynamically allocated in a Flex ring and is calculated by ibaPDA. The data volume depends on the number of analog and digital signals configured in ibaPDA and the smallest timebase configured in the ring.

For easy estimation, ibaPDA provides a simulator (32 Mbit/s Flex packet simulation) which calculates the data size per participant that can be transmitted via fiber optic link using the 32Mbit Flex protocol. The simulator is accessed via the Configuration tab.

The data volume (in bytes) of each device in the Flex ring and the timebase for the data acquisition in the ring (in µs) is needed for the calculation.

The values can be entered manually or retrieved automatically from the current configuration either by clicking the <Estimate values from current configuration> button or by selecting the corresponding link of the ibaM-FO-2IO module in the module tree.

The devices in the Flex ring and the corresponding data volumes are listed in the table on the left. Address 0 is reserved for the Ethernet channel and is not editable.

The "Flex frame utilization" section shows how much bandwidth is still available. The color of the display changes to reflect the utilization rate in the Flex ring.

  • Green: OK

  • Orange: Bandwidth for the Ethernet channel < 3 kB/s

  • Red: Too much data configured.

The data values obtained automatically are estimated first. When the configuration is applied by clicking <OK> or <Apply>, the actual data sizes are shown on the Info tab.

If too much data is configured, you can either reduce the number of signals to be measured or increase the timebase.

Simulation of the data load

Even if no devices have been connected and configured, the calculation of the telegram size can be used to calculate the expected data load in advance. However, an ibaM-FO-2IO module should be available in the system.

Open the I/O Manager in ibaPDA, click on the link of the module and select the Configuration tab.

Set the smallest planned sampling time in the "Timebase" field. Now, you can enter manually the planned or expected data volume (in bytes) in the table rows 1 to 15. With every new entry, the result values in the "Flex frame utilization" field are re-calculated.

In this way, you can estimate whether the planned number of signals can be processed on one Flex link or if you should use an additional Flex link.

Due to the large data volumes that are usually captured with ibaBM-DP, it makes sense in most cases to operate just one device on a 32Mbit Flex link.
Reserve bandwidth for Ethernet communication

The Ethernet channel (address 0) is used to transmit configuration data, to communicate with the web interface if necessary, and in particular with ibaBM-DP to display the Profibus diagnostics. If many devices are configured with a lot of signals, it is possible that only the minimum size of 1 kB/s is reserved for the Ethernet channel. This is often insufficient and the Profibus diagnostics may not be displayed as a result or communication with the web interface may become very slow.

It is now possible to reserve a fixed bandwidth for the Ethernet channel with the option "Reserve bandwidth for Ethernet communication". The default value of 4 kB/s is usually sufficient for configuration data and Profibus diagnostics.