Rockwell Automation PLC-5 Fieldbus Solutions for Integrated Architecture User Manual - Manual (Page 20)

Publication 1757-UM006A-EN-P - May 2002
1-6 The Fieldbus Communication Model
Standard Function Blocks The 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
ProcessLogix 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.
Table 1.B Function Block Specifications
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/Deriva
tive PID Control
Ratio RA Control