10. Appendix A
10.2. Standard Function Blocks
R400 Experion PKS Series A Fieldbus Interface Module User's Guide 383
July 2010 Honeywell
Overview
Th
e key to fieldbus interoperability is the User Application or Function Block
Application Process (FBAP) that defines standard function blocks that can reside in field
devices and be interconnected as a distributed process control system. A function block is
a named entity that has inputs, outputs, and parameters. It performs certain functions that
operate on its inputs and produce outputs in accordance with its assigned parameters. The
Fieldbus Foundation Function Blocks are similar in nature to the Function Blocks used to
build control strategies in the Control Builder application in the Experion system.
The Fieldbus Foundation provides the standard Function Blocks listed below for basic
control functionality. They also support additional blocks for more complex applications.
Please refer to the applicable Fieldbus Foundation specification for more information
about these additional blocks.
Function Block Abbreviation Class
Analog Input AI Input
Analog Output AO Output
Bias/Gain BG Control
Control Selector CS Control
Discrete Input DI Input
Discrete Output DO Output
Manual Loader ML Control
Proportional/Derivative PD Control
Proportional/Integral/Derivative PID Control
Ratio RA Control
Function blocks make it possible to build a control loop using fieldbus devices that
include the appropriate Function block types. For example, a pressure transmitter that
contains an Analog Input and Proportional/Integral/Derivative blocks can be used with a
valve containing an Analog Output block to form a control loop, as shown in the
following figure.
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