What is your favourite on machine distributed I/O network?

Devicenet can't be beat for its breadth of products, and ease of use. I use Devicenet everytime - (Unless of course the customer has a different spec).

With plug and play connectors and dipswitchs/thumbwheels the network is usually easy to configure. It can be tricky to setup initially but it is a time saver in the long run.

ControlNet with Remote Racks versus a distributed network of many PLCs. This eliminates the need for messaging to and fro and still maintains all the advantages of ethernet.

I know it's relatively new, but I have to say I'm very impressed with the speed, simplicity, and low cost of Ethercat.

Profibus has been my prevailing champ. Fair amount of plug and play product, easy to setup (with the right products), easy to troubleshoot (with Profitrace), and the ability to have the master in charge of parameterization is really nice.

This isn't a one network answer....but it's not a one network question either...my answer is "it depends"

Option 1: Reasonably clean environment, not a lot of large motors nearby, not a lot of human or fork truck traffic near the cell/line or the cell/line is in fenced area - EthernetI/P in the AB/Rockwell world, Profibus in the Siemens world.

Option 2: Noisy environment and/or high human/forktruck traffic, unprotected area - DeviceNet w/ AB/Rockwell, still Profibus with Siemens.

As an aside, I always prefer EthernetI/P or Profinet for controller-to-controller communications

ControlNet seems to be difficult at times but once you get acustomed to it ease of use helps versus other methods.

My favorite is definitely Modbus simple, popular and cheap. (by popular, I mean that it is supported by a lot of PLC)

I am interested to know who is using it and why see http://controlsoverload.com/questions/165/why-do-you-use-modbus