User`s guide

Function Blocks
Function Block Definition
52 UMC800 Control Builder User’s Guide Release E
1/01
Function Block Definition
Definition
A Function Block is a unit of software that performs a set of operations on its Input Signals and Function
Block parameters and produces Output Signals. These output signals can be configured as inputs to other
blocks, whose output parameters can be configured as inputs to other function blocks, and so on. By
configuring all the desired input signals and function block parameters, you develop control strategies for
both analog and digital operations.
A function block may represent a physical input or output, several inputs or outputs, an internal calculation
or an internal function such as a PID algorithm. A single controller configuration may have up to 250 user-
defined blocks. Block numbers 249 and 250 are reserved for specific status blocks.
Types of blocks
Each function block performs a set of operations that fulfills a unique purpose. For example, the Analog
Input function blocks processes the analog input data, the Analog Output function block processes Analog
outputs, and so on.
Table 14 lists the categories of function blocks and Table 15 describes each function block.
For additional Information on each Function Block, refer to the UMC800 Control Builder Function
Block Reference Guide Document # 51-52-25-64).
Function blocks such as Analog Input, Analog Output, Digital Input, and Digital Output interface with the
hardware; that is, they are the link between the controller and the input or output modules.
The Analog Input and Digital Input function blocks convert the incoming process data (like the process
variable or any digital On/Off signals from a switch) into information usable by the controller. This
incoming information is processed according to the entire function block configuration in the controller,
and is ultimately passed on to the Output function blocks.
The Analog output and Digital output function blocks convert this output information into a voltage or
current, which is fed to the corresponding output hardware (like a current output or relay).
Other function blocks are transparent to the hardware; they are purely software. They can be thought of as
the middle of the process described in the previous paragraphs, such as PID, 2 Input AND, Square Root or
Mass Flow calculations, and others.
Signal flow
The “FLOW” of information, from the input hardware to the input function blocks to the function block
configuration to the output function blocks to the output hardware, can be thought of as a river flowing
from upstream to downstream.
For example, the Analog Input function block is typically upstream of the control loop function, which is
typically upstream of the Analog Output function block. Of course, if the two function blocks are not
directly or indirectly connected, there is no flow between the two. The procedure for assigning input and
output connections is referred to as “Softwiring”.
Most function blocks have input, do a set of operations, and produce an output.