Communication protocols

Hello All

I have one question about communication protocols such as Rs485 , can , profinet , Profibus and ………… in your point of view which of them is better and why , very thanks

First, RS-485 is a wiring specification, not a protocol.

None of them are necessarily better. Profibus is widely used outside the US. Generally any protocol will do the job, and the choice is dictated by the equipment you are using and the available protocols it has. There are some advantages to a peer to peer protocol instead of a master/slave one, since peer to peer lets any device on the network issue communications commands. Profinet is simply Profibus over Ethernet.

RS485 is an electrical standard for communication wiring.

CAN and Profibus are bus type networking standards. CAN itself is a layer 2 implementation but DeviceNet is a higher level implementation using the CAN bus specifications.

Profibus is also a field bus type network. Profinet is profibus using Ethernet media.

I can state that RS485 is just physical wiring that is used by CAN or Profibus plus many others so it can not be compared to network protocols.

Better is relevant to the situation.

Very Thanks,

Really, I have to design control hardware with embedded communication protocol, in this case these are important to chose communication protocol, speed of protocol (means bit rate), distance of fields is between 100 M and some KMs, networking capability (not peer to peer), alternative media like wire wireless plc (power line carrier), cost of installation (wiring and …), and cost of hardware (means Ics and …)

Please let me know what kinds of protocol match my needs?

To a certain degree is depends on your target customer. I am assuming you are making a product for sale to others. That should be your starting point. Find out what your customer base wants or is using and support that interface.

If you are doing this for internal use then it's more wide open. I may be wrong on this but I think the CAN-based busses and Ethernet will provide the best price/performance ratio. RS-485 as a physical layer probably gives you the most flexibility. Ethernet provides alot of available components for physical linking and bridging. Profibus will have alot of overall industry support and is a pretty easy physical medium to work in.

RS-485 based systems and Ethernet will easily support wire-to-wireless transitions.

As you can see there really isn't an easy answer. Unless you have a very specific requirement any of the bus types will probably work for you.

Keith

If this is a general use automation product and you want connectivity to other systems, your first choice should be Modbus RTU. This is a master slave protocol, and is a little dated, but in the US it is the most universally accessible protocol, supported by almost every platform in one fashion or another, and is public domain.

Most of the above is also true of Profibus outside the US, but there is a PTO (Profibus Trade Organization) that you should look into.

Ethernet is the next level up from the serial protocols. ProfiNet and Modbus TCP/IP are both fairly open, but the ControlNet (more or less DeviceNet over Ethernet) is getting bigger.

As was stated above, talk to your prospective customers and find out what they want!

Hello, I'm a noob here so please excuse any improper questions and or their format.

I have just been introduced to Modbus that will be used with a Quantum PLC and talking to an ABB ACS 800. I have figured out some of the register information for the transfer, I think, but I'm having trouble identifying where the data sets are. It seems like they will be in registers 40000-40096, but I can't find any kind of data set map in the ACS 800 manual nor anything in the Modbus Adapter Module, RMBA-01.

My history has been with Allen-Bradley PLC/SLC's, Panel Views, Wondereware, and RSView Studio.

Any help would be appreciated.