Slap! I could have had a … no, not a V-8, a PROFINET backbone. That was the reaction of a student at the Greenville PROFINET one-day training class who recently installed a PROFIBUS DP backbone. Well, actually, what he wrote on the Course Evaluation form under the “In greater detail” section was: “PROFIBUS vs. PROFINET. I just installed a PROFIBUS DP backbone and lots of distributed IO… should I have used PROFINET?”
This is definitely a question worth asking and I’ll answer it here. Let’s start out adding that greater detail he requested about PROFIBUS vs. PROFINET.
We do provide a bit of a comparison between PROFIBUS and PROFINET in the course. I think we can sum up that comparison by saying that PROFINET is newer with greater speed and larger bandwidth while PROFIBUS (being older) has more products available. Here is a more detailed comparison table.
| PROFIBUS | PROFINET | |
| Organization | PI | |
| Application profiles | same | |
| Concepts | Engineering, GSDs | |
| Physical layer | RS-485 | Ethernet |
| Speed | 12Mbit/s | 100Mbit/s |
| Telegram | 244 bytes | 1440 bytes |
| Address space | 126 | unlimited |
| Technology | master/slave | provider/consumer |
| Connectivity | PA + others* | many buses |
| Wireless | Possible* | IEEE 802.11, 15.1 |
| Motion | 32 axes | 150 axes |
| Machine-to-machine | No | Yes |
| Vertical integration | No | Yes |
| # of products | thousands | hundreds |
| *not in spec, but solutions available | ||
Although this student expressed his concern in terms of “versus,” I see PROFIBUS and PROFINET as complementary. It is more often “PROFIBUS and PROFINET” than “PROFIBUS or PROFINET.” From the same organization, using the same concepts, and sharing many of the application profiles contribute to this complementary relationship. The ability to seamlessly use both in the same project cements the deal. But PROFINET is definitely more future-proof. Future-proof in terms of the technology – continuing to leverage the evolution of Ethernet. And in terms of future expansion – additional equipment with additional (perhaps unanticipated) functions, for example.
My answer to the question “I just installed a PROFIBUS DP backbone and lots of distributed IO… should I have used PROFINET?” Yes.
PROFINET would have provided this student with the future-proofing and other benefits mentioned above. But, PROFIBUS DP is a solid, reliable, proven network that is fast enough for many applications. He won’t be sorry for having used PROFIBUS, but <forehead slap> he could have had a PROFINET.
–Carl Henning
[Posted from Hanover, Germany. Stop by the PI booth in Hall 9 for a visit if you’re here.]