PROFINET IO OVERVIEW

This paper presents an overview of PROFInet IO, a high-level network for industrial automation applications. Built on standard Ethernet technologies, PROFInet IO uses traditional Ethernet hardware and software to define a network that structures the task of exchanging data, alarms and diagnostics with Programmable Controllers and other automation controllers.

PROFInet IO is one of two open Ethernet standard automation "views" from Profibus International. While PROFInet IO focuses on Programmable Controller data exchange, PROFInet CBA (Component Based Automation) focuses on distributed automation systems. PROFInet CBA provides a DCOM-based system for organizing automation systems into networks of peer devices that can automatically exchange data using predefined relationships between the interfaces of the automation components. PROFInet CBA is thoroughly discussed in another paper.

PROFInet IO is very similar to Profibus on Ethernet. While Profibus uses cyclic communications to exchange data with Programmable Controllers at a maximum speed of 12Meg baud PROFInet IO uses cyclic data transfer to exchange data with Programmable Controllers over Ethernet. As with Profibus, a Programmable Controller and a device must both have a prior understanding of the data structure and meaning. In both systems data is organized as slots containing modules with the total number of I/O points for a system the sum of the I/O points for the individual modules.

PROFInet IO uses three different communication channels to exchange data with programmable Controllers and other devices. The standard TCP/IP channel is used for parameterization, configuration and acyclic read/write operations. The RT or Real Time channel is used for standard cyclic data transfer and alarms. RT communications bypass the standard TCP/IP interface to expedite the data exchange with Programmable Controllers. The third channel, Isochronous Real Time (IRT) is the very high speed channel used for Motion Control applications. IRT is implemented using a custom ASIC and is not the subject of this paper.