I am studying about Foundation Fieldbus and it mentions one of its biggest assets is it's interoperabilty where devices from different manufactures or vendors can be attached to the fieldbus Network/System.

One of the reasons for this interoperabilty is because of the function block or the Model Block system.

I am not really clear what does the function block model means. Is it Where each function of the device is defined as a block of code in it's architecture?

Kindly advice me on the subject at hand.

 

I believe you are very close. The way I understood the function block model is that you have the blocks available as a "chunks" of code that are predefined with the blocks input/output variables. Before you decide to use them you will have to read the help associated with them and decide if you need them. Later you can call them within the function by supplying the correct type of variables.

I hope that helps,
Igor

 

Function blocks for process control have existed since computer control of the late 1960's, and to my recollection were created by George Woodley working for the Foxboro Company on the PCP88. A Function Block may be considered to be a software object with all of the object properties including a transform algorithm that takes inputs and creates outputs. Inputs to the algorithm may be drawn from either static (constant) attributes or dynamic attributes. An attribute may be linked to an attribute of another function block, may be a constant, or may be linked to a input from an HMI device. Mathematically, a function block is like a La Place transform. Programmatically a function block is somewhat like a subroutine, but is more like a separately compiled program module that is dynamically linked when the system is installed.

Function blocks are defined in the IEC 61499 standard, and Function Block Programming is one of the 4 "languages" define by the IEC standard 61131-3 Programming Languages for Programmable Logic Controllers.

Dick Caro, CAP

 

Function blocks are key to interOPERability and better yet to interCHANGEability. All the basic functions use standardized function blocks such as AI, AO, DI, DO, and PID etc. All transmitters of all types from all manufacturers have a standard AI block which is well defined. For instance, the process variable (PV) is the 7th parameter. That is, any control system or whatever can find the AI block and then the PV in the device very easily. No need to mess around with different register numbers. This now enables an instrument technician to replace a failed transmitter with another without touching the system (historical note: this was not possible with earlier versions of fieldbus systems that didn't support this very well).

See the fieldbus brochure here:
http://www.fieldbus.org/images/stories/technology/aboutthetechology/overview/fieldbus_brochure.pdf