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Introduction to ControlLogix Function Block
Function Block Programming
• Relatively new PLC language• ControlLogix only Allen-Bradley PLC family to
support function block• From IEC 1131-3 specifications
Uses of Function Block
• Process control such as PID• Drive systems
Why Function Block?
• New instructions• Advanced function block instructions have
instructions that would take many ladder rungs to create equivalent logic.
• Function block has user-defined blocks.
• Not all relay ladder logic instructions are available in function block.
• A ControlLogix routine must be 100% the same programming language.
Function Block Components
• Function block routine• Function blocks for instructions• Input and output references• Wire connectors• Dotted wire for bit data• Solid line for value data
Create a New Function Block Routine
Routine name
Description if desired
Select routine type
Function Block Routine
Continuous Task
Main Ladder Routine
Function Block Routine
Function Block Sheet
Sheet number
Coordinates Grid
Delete sheet
New sheet
Navigate between sheets
Show / hide gridSheet Name
Language Element Toolbar
Input reference
Output reference
Input wire connector
Output wire connector
Input Reference for Bit
Dotted lines identify as bit or BOOL data
Bit valueInput Reference
Input Reference for Values
Solid line signifies the tag contains a value
Bit data
Tag value
Output Reference
Output reference to tag
Dotted line signifies bit data
Bit value
Wire Connectors (1 of 3)
• Used to move function block diagram wire from one sheet to another
• Output from one sheet is an input to the next sheet
Wire Connectors (2 of 3)
Sheet One
Sheet Two
Output wire connector
Input wireconnector
Coordinates
Wire Connectors (3 of 3)
• Coordinates refer ahead to the input wire connector on the next sheet or back to the output wire connector on the previous sheet.
• 2A1 refers to sheet 2 coordinates A1.• 1C2 refers to sheet 1 coordinates C2.
Language Element ToolbarBoolean AND
Boolean OR
Boolean Excusive OR
Boolean NOT
Up / Down counter
Timer on-delay with reset
Boolean AND
Relay Ladder AND Logic
Boolean OR
Relay Ladder OR Logic
Boolean Exclusive OR
Relay Ladder Logic Excusive OR
Boolean Not
Relay Ladder NOT Logic
Adding Address Tag
Drag Wire To Target
Drag wire to target. When target changes drop wire.
Function Block Properties
Click here to go to properties.
BAND Properties Box
Parameters visible?
Monitor values
Execution order