5/12/2017
TECH-538/D.W.O. 23160
Page 130 of 189
Function Blocks Application Process (FBAP)
Overview
As mentioned before, a fieldbus network is a distributed system composed of a number of
field devices along with control and monitoring equipment integrated into the physical
arrangement of a plant or factory. Fieldbus devices operate together to provide Input,
Output and Control of automated processes and operations. The Foundation fieldbus
protocol provides a framework for defining these systems as an assortment of physical
devices interconnected by a fieldbus network. The way the physical devices perform their
proper role as a portion of the total system operation is by assigning their physical inputs and
outputs to one or more software defined function blocks. A specific layer of the FF
specification, called Function Block Application Process (FBAP) contains all the definitions and
interaction rules for the Function Blocks. (See References (FOUNDATION™ Specification,
Function Block Application Process Part 1 – FF-890, Rev FS 1.10) and (FOUNDATION™
Specification, Function Block Application Process Part 2 – FF-891, Rev FS 1.10))
Function Blocks are structures with defined behavior used to represent different types of
functions that the device performs. FF has defined a standard set of function block classes,
such as input, output, control, and computation function blocks. The next figure illustrates a
simple control loop with an AI FB linked to a PID FB whose signal is controlling the position of
the control valve via the AO FB. Both the PID and AO may reside within the control valve.
For a complete list of parameters of each block implemented in the ICoT, please refer to the
Section 11.4 (Block Parameters Reference).
Figure 11-1 – Example of a Function Block Application: AI-PID-AO
