Allen Bradley PLC Tag

Help Contents


The Allen Bradley PLC Tag PLC Device Tag Icon provides a logical link to an Allen Bradley PLC Device. The tag supports: ControlLogix, CompactLogix, Micro820, Micro850, Micro870, MicroLogix, SLC and PLC-5.

Configuration Properties

The Allen Bradley PLC Tag supports the configuration properties of the PLC Device Tag with RTC, plus these properties:

Property Type Version Description
Channel Reference 2.2 A reference to one of the following:
DestinationNode USINT 2.2 The DF1 destination node of the PLC. The valid range is 0-254. This property is only used when the Channel property refers to an Allen Bradley Serial Communication Channel.
PLCType USINT 3.41 The type of this PLC. Choose one of the following:
  • MicroLogix, SLC and PLC-5.
  • CompactLogix, ControlLogix.
RoutePath WSTRING 3.41 For tag based PLC Devices (CompactLogix, ControlLogix, Micro820, Micro850, Micro870) the communication path to get to the CPU. For more information see RoutePath Configuration Property below.

RoutePath Configuration Property

The RoutePath configuration property is used with tag based (ControlLogix, CompactLogix, Micro820, Micro850, Micro870) PLC Devices. The configuration property tells the communication end point how to route messages to the CPU.

The RoutePath property consists of a sequence of numbers separated by commas. For example:


This tells the communication end point to forward the message to slot 0 on the backplane.

Recommended values for RoutePath:

Serial Port on CPU Leave the property blank.
Ethernet Module 1,n The value n is the slot number of the CPU.

More complex route paths are possible. For example, multiple hops across different networks.

Tag Commands

The Allen Bradley PLC Tag supports the tag commands of the PLC Device Tag with RTC plus these commands:

Tag Command Version Description
DirectWriteWord 2.3 Directly writes one or more words to an address in the PLC.
DirectWriteBit 2.3 Directly writes a single bit to an address in the PLC.
Refresh 3.15 Requests an immediate refresh of the I/O Data Point Tags associated with the PLC.

Relationships to Other Tag Types

The Allen Bradley PLC Tag builds on the features of these tag types:

Further Information

Allen Bradley Serial Communication Channel

To learn about Allen Bradley serial communication channels.

Allen Bradley Ethernet Communication Channel

To learn about Allen Bradley Ethernet communication channels.

Allen Bradley Register Blocks

To learn about reading blocks of data from an Allen Bradley PLC.

Alarm Conditions

To learn about abnormal conditions in SCADA applications.


For the meaning of terms used in Fernhill SCADA.