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