Diffrence between buses


Thread Starter


I need the diffrence between general bus that used in industry. the diffrence in protocol, hardware, software...

James Ingraham

For a summary description, Synergetic/Lantronix has a Fieldbus Comparison Chart that is always my first stop for checking the differences among fieldbuses. http://www.synergetic.com/compare.htm

To get more specific data on the buses you mentioned:

modbus: www.modbus.org
fieldbus: There's no such thing; presumably you mean FOUNDATION Fieldbus. www.fieldbus.org
canbus: www.canopen.org
profile bus: Again, so such thing. Guessing you mean ProfiBus (PROcess FIeldBUS). www.profibus.com

-James Ingraham
Sage Automation, Inc.
There are many differences between them. Of course all of them pass data from A to B, but they do it differently and therefore each has unique benefits and disadvantages depending on the application. What is your application? Based on this I can perhaps recommend what may be best for you.

Modbus (Modbus/RTU, Modbus/ASCII, ModbusPlus, Modbus/TCP): Modbus/RTU is most common and usually uses RS232 or RS485 media. Very simple, compatible with more devices and software than anything else, but a bit limited and require some manual work. ModbusPlus has proprietary hardware and some more capability but is not so widely used. Modbus/TCP uses Ethernet media and TCP/IP.

Fieldbus (I suppose you mean FOUNDATION(tm) Fieldbus (H1 or HSE)): Your best choice for process control such as regulatory control of pressure, temperature, level and flow etc. Very powerful. H1 Fieldbus is used with field instruments. HSE Fieldbus is based on Ethernet and is used among linking devices, controllers and workstations.

CAN bus: CAN itself is just the physical media. However, it is the platform on which many network technologies are built. E.g. DeviceNet, SDS, SafetyBUS-P etc. You need to pick one of them. CAN bus based networks is ideal for simple on/off components such as optical and proximity switches, buttons, starters, and solenoids etc.

Profibus (Profibus-FMS, Profibus-DP, Profibus-DPv1, Profibus-DPv2, Profibus-PA, ProfiSafe, ProfiDrive, and PROFInet) Profibus-FMS, Profibus-DP, Profibus-DPv1, Profibus-DPv2, ProfiSafe, and ProfiDrive use RS485 media. Profibus-PA uses same media as H1 Fieldbus. PROFInet uses TCP/IP on Ethernet. Profibus-PA is suitable for process control instruments whereas Profibus-DP, Profibus-DPv1, Profibus-DPv2, ProfiSafe, ProfiDrive, are best suited for connecting I/O to PLC. Profibus-FMS and PROFInet connect PLCs to workstations.

To learn about Foundation Fieldbus and Profibus-PA take a look at the book "Fieldbuses for Process Control: Engineering, Operation, and Maintenance" (buy online in hardcopy or download immediately in softcopy). Mind the line wrap, make sure to get the complete path all the way to the 6: http://www.isa.org/Template.cfm?Section=Shop_ISA&Template=/Ecommerce/Product Display.cfm&ProductID=3036 You can even download chapter 1 for free in softcopy form. Mind the line wrap, make sure to get the complete path all the way to the 5: http://www.isa.org/Template.cfm?Section=Shop_ISA&template=/Ecommerce/Product Display.cfm&ProductID=4585

Jonas Berge
[email protected]