Rockwell Automation T6200 Compressor Anti-Surge and Capacity Controller - Manual (Page 138)

Configuration
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Function Block Diagram (FBD)
A Function Block Diagram is a data flow between constant expressions or variables and
operations represented by rectangular blocks. Operations can be basic operations, function calls, or
function block calls.
The name of the operation or function, or the type of function block is written within the block
rectangle. In case of a function block call, the name of the called instance must be written upon the
block rectangle, such as in the example below:
The data flow may represent values of any data type. All connections must be between input and
outputs points having the same data type. In case of an analog alarm (such as ALARM_XM,
ALARM_FB see below, etc.), the input to the function block is a real value and the output is a
boolean connection.
The following is an example of alarm management (MGT) functions with suppression of process
alarms (SuppPA). The connections consist of Real, Boolean and Integer data.
The data flow must be understood from the left to the right and from the top to the bottom.
It is possible to use labels and jumps to change the default data flow execution.