Producer/Consumer ethernet fieldbus protocols


Thread Starter


Does anyone know of ethernet fieldbus products that use a Producer/Consumer protocol?

I have to determine the difference between Producer/Consumer and Client/Server protocol in order to evaluate the response time in Ethernet-based automation systems using Producer/consumer protocols.

A best understanding of this protocol (and how the RIOM and PLCs used it) will allow me to model the different delays. For example, is the RIOM produces data at a determinate rate? and is the Ethernet board of PLC has a polling cycle?

Thank you.
Thank you Dick Caro,

Now I know that the I/O modules in producer/consumer model can produce data (at the Requested Packet Interval (RPI)) without having been polled by a controller first..! but what about receiving the orders from the controller? does the I/O module take into account immediately the order when it arrives or has a scan period? same question about the controller when data arrive from I/O modules?
The purpose of Producer/Consumer or Publish/Subscribe (Foundation Fieldbus) is to transmit synchronous data needed for many purposes including closed loop control. Typically, a sensor or an RTU sends the data on a schedule. Any other action including Polling may still take place, even including the datum value which has been scheduled. Produced or Subscribed data messages typically have priority over polled queries in order to meet time-critical schedules. The receiver only needs to respond to the new data as it arrives.

In Foundation Fieldbus, datum arrival does not initiate anything other than buffering. For a control loop, there is a master scheduler called LAS (Link Active Schedule) that synchronizes the publishing and control cycles to make sure that the datum arrives at the controller just-in-time for the control cycle. I am not sure that this synchronization function is available with CIP as implemented for the Rockwell PLCs.