Difficulties caused by all kinds of Ethernet protocols

- Dec 15, 2018-

Manufacturers expect to achieve more and more automation processes in the system, so they must take into account the requirements of IT system for open data access and the real-time requirements of industrial control systems. Industrial Ethernet systems require high certainty and reliability. In many factory automation applications, because Ethernet has higher bandwidth and can link to enterprise network, it has replaced the traditional serial "fieldbus" connection, but Ethernet itself does not have the deterministic response of fieldbus system. 


In order to overcome this limitation, each major industry OEM has made its own Ethernet protocol, and has since become a widely used open standard: PROFINET, Ethernet / IP,EtherCAT,ModbusTCP and several other standards. Some of these protocols are fully compatible with standard TCP/IP Ethernet networks, while others have modified data links, networks and / or transport layers (layers 2-4 in the OSI model) to achieve deterministic performance. 

Unfortunately, product makers have yet to agree on a common industrial Ethernet standard; on the contrary, the field is fragmented, with more than 30 standards deployed in factories. Although these protocols can coexist with standard Ethernet, they cannot interoperate with each other in a definitive manner. Many leading manufacturers have defined a specific industrial Ethernet standard to meet their needs, often from one of their existing serial-based fieldbuses. 

Most industrial Ethernet standards require a separate device solution. Fig. 1 illustrates a solution that includes a microcontroller unit or a microprocessor unit and a separate industrial Ethernet device, a media access controller. The MAC supports real-time Ethernet frame processing, which is technically called "instant" or "through" frame processing. Therefore, most industrial Ethernet standards require the application of ASIC or FPGA to handle real-time Ethernet frame processing.