Three Things Every Beginner Must Know About PROFINET IO

It was 3:00 AM and I couldn’t sleep. My wife had made her way to my side of the bed and was pinning my arm down and snoring. I wanted to get up and read to see if that would help, but I knew that if I wiggled too much, she’d wake up. So, I turned on the TV and began scrolling. I stumbled across a soccer match and figured that would put me to sleep. I also began scrolling on my phone, only half paying attention to the match. At one point I looked up and thought: Huh, they usually don’t tackle each other this much in soccer. What am I even watching? From that moment on, I was hooked on the Australian Football League (AFL)

Anyone can become a fan of something as they learn more about it, as happened with me and the AFL. I’m also a fan of PROFINET IO. Now, I am far from being an expert but the more familiar I get with PROFINET IO, the more I like it, which is why it’s the topic of this blog. As you begin a brand-new adventure with PROFINET IO, here are the three things I think you have to know.

#1 Network Representation

Unlike more common industrial protocols in the US, PROFINET IO uses slots, subslots, and channels to represent data in the network. Each subslot is assigned a number of I/O points or channels. A channel is the PROFINET IO term which refers to one physical discrete input, discrete output, analog input or analog output. Do note that a device can have almost any number of slots, subslots and channels. Every slot and subslot, with the exception of slot zero, contains alarm, status and diagnostic data. Even though PROFINET IO devices and GSD files refer to “slot zero”, there is no slot zero. The first I/O slot of a device is slot one. Instead of referring to an actual slot, slot zero refers to the device itself. No I/O data is contained in slot zero. In place of I/O data, slot zero manages all the generic device data, like the vendor name, product catalog number, software and hardware version information and other similar information.

#2 Device Classification

There are three PROFINET IO device classes: IO-controllers, IO-devices and IO-supervisors. Controllers are the pieces of equipment responsible for executing automation programs. Controllers, functionally similar to a PROFIBUS class 1 master, exchange data with IO-devices. Devices are sensor and/or actuator equipment connected to the controller via an Ethernet connection. To help you better understand, think of a device as a PROFIBUS slave. IO-supervisors are HMIs, PCs or other commissioning, monitoring or diagnostic analysis devices.

#3 Alarm and Diagnostic Data

These two types of PROFINET IO data are regularly mixed up by rookies. If you understand the difference, you have an instant leg up on everyone else. Diagnostic data is data associated with a channel or I/O point. Diagnostic data is always transferred acyclically using record data communications over the non-real time (NRT) channel. An IO-supervisor must specifically request the diagnostic data from the device using record data object (RDO) services.

Alarm data is quite different. While one type of alarm is an alert that diagnostic data exists on a specific channel, there are many more reasons why a device would signal an alarm. Alarms are signaled when a module or submodule is plugged in or pulled out, when the wrong module or submodule is plugged in, when a process limit is reached, when the device state changes or for many other reasons. The biggest difference here is that unlike diagnostic data, alarm data is sent exclusively on the real time channel and only to the programmable controller linked to the module.

For assistance implementing PROFINET IO into your factory operation, give us a buzz at 1-800-249-1612, or contact us via our website! We have a number of solutions available that will fit your factory needs. In the meantime, I better make a pot of coffee. I hear there is going to be an exciting Australian football game on tonight and I have to be awake for it.