If Modbus is like “Batman” of protocols, then Profibus is the Superman – lean and fast.
Profibus was developed in the 1990s to archive all industrial communication needs for both Industrial and process automation
As with Modbus, there are a number of different names related to this protocol:
What is Profibus?
- Now visualizing or think Profibus as a Manual or study book with many chapters or a different section. The book we can say Profibus DP(Decentralized Peripheral).
- The book or Manual Different chapter is like Profibus PA(Process Automation), Profisafe, Profidrive for high-speed drive application.
- Now there would be the second book by same publisher or authors called profinet with many chapters also include profisafe, Profidrive
- We already understand what is Profibus Now We Understand How its Work
How Profibus Work ?
- Profibus is also a master-slave protocol to allow for multiple masters. all device perform startup sequence when they join a network. slave maintains failsafe timer.
- If the master does not talk with slave during the certain time limit. the slave goes in a safe state. the master again performs startup sequence again further data exchange occurs
- the watchdog timer in the master ensures that all communications performed in the certain time limit. every master pass token(packets) to
- the next master when own slave communication complete.
- Profinet is working on the same principle as Profibus, but Profinet designed to take advantage of Profibus and Using Modbus TCP/IP
Physical Layer :
- Profibus DP Using physical layer RS-485 but not like Modbus.it extends RS-485 specification. Physical layer required only two wire with speed as Fast as 12 Megabits per second the Profibus specification also standardizes the connectors to be used
- Profibus PA Using physical layer called IEC 61158-2, Manchester Encoded, bus-powered, intrinsically safe (MBP-IS).
- This physical layer provides power and communications on the same two wires.
the concept has a big advantage when it comes to installation costs. Working with hazardous environments,
- there are two approaches: The power going to the instrument in the hazardous area, or the power going out into the hazardous area can be limited.
- The containment method is the traditional one and the one that is required for Modbus. It uses a metal current conveyance and seals to “contain” the energy. Both the conduit and seals are expensive to buy and install.
- The second approach is used by Profibus PA. It limits the power going to the field and is considered safe. With it, no conduits or seals are needed (except maybe at the starting cabinet), resulting in significant cost savings.