What is MultiFieldbus?

Changing a PLC on a system to meet a customer’s preference can have significant implications for the system design. This can leave the customer asking common questions, such as:

• Will the network protocol need to change?
• Will existing devices have a variant that supports the other protocol?
• What is the impact on the electrical design and software, and what additional validation will be required?

One way manufacturers are addressing this problem is through the introduction of MultiFieldbus remote I/O devices. These work exactly like traditional I/O devices, but the ‘header’ (or controller) is configurable to communicate through a variety of different fieldbus communication protocols. You can safely standardise a system around these I/O devices and then configure them through software for whichever communication protocol the system’s PLC needs.

For a control system manufacturer, there are significant benefits:

• The electrical design for the I/O can be standardised, resulting in no redesign work to accommodate different protocols.
• The parts are all the same, simplifying materials costs. Plus allowing parts to be held in stock to reduce equipment lead times.
• Common diagnostics simplify troubleshooting and support.

Example Application

We recently had a project that made use of the Siemens SIMATIC MultiFieldbus ET200 I/O system. The SIMATIC MultiFieldbus supports the PROFINET, Ethernet/IP, and Modbus/TCP communication protocols. Our customer wanted a duplicate of an existing system, where a tank controlled by ET200 remote I/O was connected to a Siemens S7-1500 over Profinet. They also wanted the additional functionality of connecting this tank to their DCS. Their DCS, however, only supported Ethernet/IP.

The MultiFieldbus ET200 was the ideal solution. In the device assembly, the MultiFieldbus interface module replaces the Siemens standard PROFINET-only one. The remainder of the device isn’t configured any differently. Therefore we were able to minimise the redesign of the tank remote I/O, as only a change to the interface module was required. We were able to configure the module as either an Ethernet/IP node to communicate with the customer’s DCS or a Profinet node to communicate with our PLC.

The interface module is programmed to the required communication protocol using the MultiFieldbus Configuration Tool (MFCT) software, which is freely available from Siemens. In the event of a device failure, a replacement can be installed, configured, and deployed easily, without the need for complicated or costly programming software. The tank control system we designed can now be deployed on networks running PROFINET, Ethernet/IP, or Modbus/TCP with only a simple parameter change and no modifications to the hardware required.