Allen-Bradley Route

Connect to Rockwell PLCs by Tag Name

The ALLEN_BRADLEY route connects Coreflux to Rockwell Automation PLCs using symbolic tag names over EtherNet/IP (libplctag). Define an ALLEN_BRADLEY_CONFIG block, add TAGs with PLC tag addresses, and publish each data point to its own MQTT topic — with optional scaling, units, deadband, and bidirectional writes.

Like reading labels on a control panel. Instead of numeric register addresses, you use the same tag names you see in Studio 5000 — MainCounter, Program:MainProgram.Temperature, Motor1.Speed.

For explicit CIP paths (4.100.3.0), use the EtherNet/IP route instead. This route is for symbolic tag-name access; EtherNet/IP is for Class/Instance/Attribute addressing.

Route and config aliases

Alias	Canonical form
`TYPE AB` or `TYPE ALLENBRADLEY`	`TYPE ALLEN_BRADLEY`
`ADD AB_CONFIG`	`ADD ALLEN_BRADLEY_CONFIG`

Key capabilities

Symbolic tag names — controller-scoped, program-scoped, UDT members, and arrays
Multiple PLC families — ControlLogix, CompactLogix, Micro800, MicroLogix, PLC5, SLC500
TAG-based polling — per-point MQTT topics with configurable intervals
Bidirectional writes — WRITABLE tags with DESTINATION_TOPIC
Engineering units — SCALING, OFFSET, UNIT, DECIMAL_PLACES, min/max clamping
Publish modes — VALUE_ONLY (default) or JSON with quality metadata

Quick Start

Poll a controller tag
Program-scoped tags
Read and write
Micro800

Read a controller-scoped DINT counter every second:

DEFINE ROUTE ControlLogixPLC WITH TYPE ALLEN_BRADLEY
    ADD ALLEN_BRADLEY_CONFIG
        WITH IP "192.168.1.10"
        WITH DEVICE_FAMILY 0
        WITH PATH "1,0"
    ADD MAPPING ProductionData
        WITH EVERY 1 SECOND
        ADD TAG ProductCounter
            WITH ADDRESS "MainCounter"
            WITH DATA_TYPE "DINT"
            WITH SOURCE_TOPIC "production/counter"

Read tags inside a specific program with units and deadband:

DEFINE ROUTE ControlLogix WITH TYPE ALLEN_BRADLEY
    ADD ALLEN_BRADLEY_CONFIG
        WITH IP "192.168.1.20"
        WITH DEVICE_FAMILY 0
    ADD MAPPING ProcessControl
        WITH EVERY 500 MILLISECONDS
        ADD TAG ReactorTemp
            WITH ADDRESS "Program:MainProgram.Temperature"
            WITH DATA_TYPE "REAL"
            WITH UNIT "°C"
            WITH DECIMAL_PLACES 2
            WITH DEADBAND 0.5
            WITH SOURCE_TOPIC "process/reactor/temperature"

Poll a setpoint and accept MQTT writes to update it:

DEFINE ROUTE TemperatureControl WITH TYPE ALLEN_BRADLEY
    ADD ALLEN_BRADLEY_CONFIG
        WITH IP "192.168.1.60"
        WITH DEVICE_FAMILY 0
    ADD MAPPING ControlLoop
        WITH EVERY 1 SECOND
        ADD TAG TempSetpoint
            WITH ADDRESS "TempSetpoint"
            WITH DATA_TYPE "REAL"
            WITH UNIT "°C"
            WITH MIN_VALUE 0.0
            WITH MAX_VALUE 100.0
            WITH SOURCE_TOPIC "control/temperature/setpoint"
            WITH WRITABLE "true"
            WITH DESTINATION_TOPIC "control/temperature/setpoint/write"

Read built-in I/O on a Micro800 controller:

DEFINE ROUTE Micro800PLC WITH TYPE ALLEN_BRADLEY
    ADD ALLEN_BRADLEY_CONFIG
        WITH IP "192.168.1.70"
        WITH DEVICE_FAMILY 4
    ADD MAPPING Micro800Data
        WITH EVERY 1 SECOND
        ADD TAG DigitalIn
            WITH ADDRESS "_IO_EM_DI_00"
            WITH DATA_TYPE "BOOL"
            WITH SOURCE_TOPIC "micro800/input0"

Connection Configuration

ALLEN_BRADLEY_CONFIG Parameters

Parameter	Required	Default	Description
`IP`	Yes	—	PLC IP address
`DEVICE_FAMILY`	No	`0`	Device family code (0–6, see table below)
`PORT`	No	`44818`	EtherNet/IP port. Micro800 (`DEVICE_FAMILY 4`) passes this to libplctag as `gateway=IP:PORT`. Other families use the default EIP port via libplctag.
`SLOT`	No	`0`	Parsed for documentation/legacy parity. libplctag uses `PATH`, not `SLOT`, for backplane routing — set the CPU slot in `PATH` (for example `"1,0"`).
`PATH`	No	`"1,0"`	Routing path to the PLC (format: `backplane,slot`). Passed to libplctag.
`TIMEOUT`	No	`5000`	Per-tag read/write timeout in milliseconds

The config block may be declared as ADD ALLEN_BRADLEY_CONFIG or ADD AB_CONFIG — both are equivalent.

ConnectAsync marks the route ready; libplctag opens a transport per tag read/write. -checkRouteConnection confirms the route is loaded but does not probe the PLC — verify connectivity with polling or a test read.

Device Family Codes

Code	Family	Use when
`0`	ControlLogix / CompactLogix	1756-L6x, L7x, L8x, 1769-Lxx (most common)
`1`	PLC5	1785-L series (legacy)
`2`	SLC500	1747-L series (legacy)
`3`	ControlLogix PLC5	Mixed environment
`4`	Micro800	2080-LC series
`5`	MicroLogix	1766, 1764 series
`6`	Omron	NJ/NX with CIP support

Connection Examples

ControlLogix / CompactLogix
MicroLogix
Through backplane
Micro800

Standard backplane path to CPU in slot 0:

ADD ALLEN_BRADLEY_CONFIG
    WITH IP "192.168.1.100"
    WITH DEVICE_FAMILY 0
    WITH PATH "1,0"
    WITH TIMEOUT 5000

MicroLogix 1100/1400:

ADD ALLEN_BRADLEY_CONFIG
    WITH IP "192.168.1.50"
    WITH DEVICE_FAMILY 5
    WITH TIMEOUT 5000

CPU in slot 2 on backplane 1:

ADD ALLEN_BRADLEY_CONFIG
    WITH IP "192.168.1.100"
    WITH DEVICE_FAMILY 0
    WITH PATH "1,2"
    WITH TIMEOUT 5000

Micro800 — PATH is usually omitted:

ADD ALLEN_BRADLEY_CONFIG
    WITH IP "192.168.1.70"
    WITH DEVICE_FAMILY 4
    WITH TIMEOUT 5000

Tag Addressing

Allen-Bradley PLCs use tag-based addressing (not register numbers). Tag names are case-sensitive.

Scope	Format	Example
Controller	`TagName`	`MainCounter`
Program	`Program:ProgramName.TagName`	`Program:MainProgram.Counter`
Array element	`TagName[index]`	`Temps[5]`
UDT member	`UDTInstance.Member`	`Valve1.Status`
Nested UDT	`Parent.Child.GrandChild`	`Tank1.Level.Current`
I/O tags	`Local:Slot:Type.Data[index]`	`Local:1:I.Data[0]`

Tag naming rules

Letters, numbers, and underscore only
Must start with a letter or underscore
Case-sensitive
No spaces

# Valid
WITH ADDRESS "MainCounter"
WITH ADDRESS "Program:MainProgram.Temperature"
WITH ADDRESS "Valve1.Status"
WITH ADDRESS "Temps[5]"

Data Types

Coreflux `DATA_TYPE`	AB type	Notes
`BOOL`	BOOL	Boolean
`SINT`	SINT	Signed 8-bit
`USINT` / `BYTE`	USINT	Unsigned 8-bit
`INT`	INT	Signed 16-bit
`UINT` / `WORD`	UINT	Unsigned 16-bit
`DINT`	DINT	Signed 32-bit
`UDINT` / `DWORD`	UDINT	Unsigned 32-bit
`LINT`	LINT	Signed 64-bit
`ULINT` / `LWORD`	ULINT	Unsigned 64-bit
`REAL` / `FLOAT`	REAL	32-bit float
`LREAL` / `DOUBLE`	LREAL	64-bit float — MQTT values round to `DECIMAL_PLACES` (default `2`)
`CHAR`	CHAR	Single character
`WCHAR`	WCHAR	Wide character
`STRING`	STRING	See encoding notes below
`TIME`	TIME	Duration in ms — published as `T#XdXhXmXsXms`
`DATE`	DATE	Date value
`TOD`	TOD	Time of day

STRING encoding

Depends on DEVICE_FAMILY:

ControlLogix / CompactLogix (default): 4-byte DINT length prefix + up to 82 ASCII characters
Micro800: 1-byte length prefix + characters

Set STRING_SIZE for the maximum string buffer size when needed.

TIME encoding

Raw value is a signed 32-bit millisecond count. MQTT publishes Allen-Bradley-style duration strings (for example T#1h1m1s1ms).

TAG Configuration

Every polled data point is an ADD TAG inside an ADD MAPPING block.

Complete TAG Example

ADD TAG MotorSpeed
    WITH ADDRESS "Motor1.ActualSpeed"
    WITH ADDRESS_TYPE "SYMBOL"
    WITH DATA_TYPE "REAL"
    WITH SOURCE_TOPIC "plc/motor1/speed"
    WITH SCALING 1
    WITH OFFSET 0
    WITH UNIT "RPM"
    WITH DECIMAL_PLACES 2
    WITH MIN_VALUE 0
    WITH MAX_VALUE 3600
    WITH DEADBAND 10
    WITH PUBLISH_MODE "JSON"
    WITH DESCRIPTION "Motor 1 actual speed in RPM"

TAG Parameters

Address and data type

string

required

PLC tag name — controller-scoped (MainCounter), program-scoped (Program:MainProgram.Counter), UDT member (Valve1.Status), or array (Temps[0]).

string

SYMBOL (default) or PATH.

string

required

Logix data type: BOOL, SINT, INT, DINT, LINT, USINT, UINT, UDINT, ULINT, REAL, LREAL, STRING, TIME, etc.

integer

Maximum string buffer size for STRING tags. Default: 256.

Value transformation

decimal

Multiply the parsed value after read. Alias: SCALING_FACTOR. Default: 1.0.

decimal

Add after scaling. Default: 0.0.

string

Engineering unit (for example °C, bar, RPM). Included in JSON publish mode.

integer

Rounding precision for float MQTT payloads. Default: 2.

Filtering

double

Clamp minimum allowed value (especially for writable tags).

double

Clamp maximum allowed value.

double

Suppress MQTT publish when the change is below this threshold. Default: 0.0.

Publishing and writes

string

required

MQTT topic where polled values are published.

string

VALUE_ONLY (default) or JSON (value, unit, quality, timestamp, description).

boolean

When "true", subscribe to DESTINATION_TOPIC and write incoming MQTT values to the PLC.

string

MQTT topic to receive write commands. Required when WRITABLE is "true".

string

Human-readable description (included in JSON publish mode).

Publish Modes

VALUE_ONLY (default) — publishes just the scaled value:

JSON — metadata wrapper when explicitly set:

{
  "tag_name": "SafetyPressure",
  "value": 8.456,
  "unit": "bar",
  "quality": "GOOD",
  "timestamp": "2025-12-17T10:30:45.123Z",
  "description": "Critical safety pressure sensor"
}

Event-Based Operations

For on-demand tag reads and writes (not continuous polling), add an ADD EVENT block. Publish any message to SOURCE_TOPIC to trigger the operation; results appear on DESTINATION_TOPIC.

Query Parameters

Parameter	Description	Example
`operation`	`READ` or `WRITE`	`READ`
`variable`	PLC tag name	`Program:MainProgram.Counter`, `MainCounter`
`data_type`	Logix data type	`DINT`, `REAL`, `BOOL`
`value`	Value to write (WRITE only)	`42`, `75.0`

Read Example

ADD EVENT ReadOnDemand
    WITH SOURCE_TOPIC "ab/commands/read"
    WITH DESTINATION_TOPIC "ab/responses/read"
    WITH QUERY "{operation: READ, variable: Program:MainProgram.Counter, data_type: DINT}"

Write Example

ADD EVENT WriteSetpoint
    WITH SOURCE_TOPIC "ab/commands/write"
    WITH DESTINATION_TOPIC "ab/responses/write"
    WITH QUERY "{operation: WRITE, variable: TIC100.SP, data_type: REAL, value: 150.0}"

Examples

Multiple data types
UDT members
Array elements
Control loop
Scaled analog

Monitor BOOL, DINT, and REAL tags in one mapping:

DEFINE ROUTE ProductionLine WITH TYPE ALLEN_BRADLEY
    ADD ALLEN_BRADLEY_CONFIG
        WITH IP "192.168.1.30"
        WITH DEVICE_FAMILY 0
    ADD MAPPING MachineMonitor
        WITH EVERY 1 SECOND
        ADD TAG MachineRunning
            WITH ADDRESS "MachineStatus.Running"
            WITH DATA_TYPE "BOOL"
            WITH SOURCE_TOPIC "machine/status/running"
        ADD TAG ProductCount
            WITH ADDRESS "ProductionCounters.TotalCount"
            WITH DATA_TYPE "DINT"
            WITH SOURCE_TOPIC "machine/production/total"
        ADD TAG LineSpeed
            WITH ADDRESS "LineSpeed"
            WITH DATA_TYPE "REAL"
            WITH UNIT "units/min"
            WITH SOURCE_TOPIC "machine/speed"

Read User-Defined Type structure members:

DEFINE ROUTE UDTAccess WITH TYPE ALLEN_BRADLEY
    ADD ALLEN_BRADLEY_CONFIG
        WITH IP "192.168.1.40"
        WITH DEVICE_FAMILY 0
    ADD MAPPING ValveControl
        WITH EVERY 500 MILLISECONDS
        ADD TAG Valve1Position
            WITH ADDRESS "Valve1.Position"
            WITH DATA_TYPE "INT"
            WITH UNIT "%"
            WITH SOURCE_TOPIC "valves/valve1/position"
        ADD TAG Valve1Status
            WITH ADDRESS "Valve1.Status"
            WITH DATA_TYPE "BOOL"
            WITH SOURCE_TOPIC "valves/valve1/status"

Read specific array indices:

DEFINE ROUTE ArrayData WITH TYPE ALLEN_BRADLEY
    ADD ALLEN_BRADLEY_CONFIG
        WITH IP "192.168.1.50"
        WITH DEVICE_FAMILY 0
    ADD MAPPING ArrayMonitor
        WITH EVERY 1 SECOND
        ADD TAG Zone1Temp
            WITH ADDRESS "ZoneTemperatures[0]"
            WITH DATA_TYPE "REAL"
            WITH UNIT "°C"
            WITH SOURCE_TOPIC "zones/zone1/temperature"
        ADD TAG Zone2Temp
            WITH ADDRESS "ZoneTemperatures[1]"
            WITH DATA_TYPE "REAL"
            WITH UNIT "°C"
            WITH SOURCE_TOPIC "zones/zone2/temperature"

Read process value and write setpoint from MQTT:

DEFINE ROUTE ControlLoop WITH TYPE ALLEN_BRADLEY
    ADD ALLEN_BRADLEY_CONFIG
        WITH IP "192.168.1.100"
        WITH DEVICE_FAMILY 0
    ADD MAPPING TempControl
        WITH EVERY 200 MILLISECONDS
        ADD TAG PV
            WITH ADDRESS "TIC100.PV"
            WITH DATA_TYPE "REAL"
            WITH SOURCE_TOPIC "control/tic100/pv"
            WITH UNIT "°F"
        ADD TAG SP
            WITH ADDRESS "TIC100.SP"
            WITH DATA_TYPE "REAL"
            WITH SOURCE_TOPIC "control/tic100/sp"
            WITH UNIT "°F"
            WITH WRITABLE "true"
            WITH DESTINATION_TOPIC "control/tic100/sp/set"
            WITH MIN_VALUE 32
            WITH MAX_VALUE 212

Scale a 4–20 mA sensor to engineering units:

DEFINE ROUTE AnalogSensors WITH TYPE ALLEN_BRADLEY
    ADD ALLEN_BRADLEY_CONFIG
        WITH IP "192.168.1.80"
        WITH DEVICE_FAMILY 0
    ADD MAPPING AnalogData
        WITH EVERY 500 MILLISECONDS
        ADD TAG Pressure
            WITH ADDRESS "AI_Pressure"
            WITH DATA_TYPE "REAL"
            WITH UNIT "bar"
            WITH DECIMAL_PLACES 3
            WITH DEADBAND 0.01
            WITH SOURCE_TOPIC "sensors/pressure"

Best Practices

Choose the correct device family

Use DEVICE_FAMILY 0 for ControlLogix and CompactLogix (most common), 4 for Micro800, and 5 for MicroLogix. Legacy PLC5/SLC500 families (1/2) only for existing installations.

Program scope

Controller-scoped tags use the name alone (GlobalCounter). Program-scoped tags need the full prefix: Program:MainProgram.LocalCounter.

PATH vs SLOT

Set the CPU slot in PATH ("1,0" for backplane 1, slot 0). SLOT is kept for legacy parity but libplctag routes via PATH.

Writable tags

Use WRITABLE "true" with MIN_VALUE / MAX_VALUE on setpoints. Ensure the PLC is in Remote Run mode for writes to succeed.

Deadbands and polling

Use DEADBAND on noisy analog values. Match EVERY to how fast the value changes — 500 ms for critical data, 1–5 s for slow status.

Troubleshooting

Connection failed

Verify IP with ping
Confirm port 44818 is open
Ensure PLC is powered on and in RUN mode
Check DEVICE_FAMILY matches your controller type
Increase TIMEOUT on slow networks
Remember: -checkRouteConnection does not probe the PLC — use a polling TAG to verify

Tag not found

Tag names are case-sensitive — match Studio 5000 exactly
Program-scoped tags need Program:ProgramName.TagName (not ProgramName:Tag)
Verify the tag exists in Controller Tags or Program Tags in Studio 5000
For UDTs, include the member: Valve1.Status not Valve1
For arrays, include the index: Temps[0] not Temps

Path errors

Use PATH "1,0" for standard backplane routing (backplane, slot)
For Micro800, omit PATH or leave it unset
Multi-hop paths use comma-separated segments: "1,2,2,1" through bridge modules

Micro800 issues

Set DEVICE_FAMILY 4
Use Micro800 I/O tag names (_IO_EM_DI_00, _IO_EM_AI_00)
STRING uses 1-byte length prefix (not ControlLogix 4-byte format)

Write operations fail

Set WRITABLE "true" and provide DESTINATION_TOPIC
PLC must be in Remote Run mode
Verify DATA_TYPE matches the PLC tag definition
Check value is within MIN_VALUE / MAX_VALUE if set

Data type mismatch

Match PLC types exactly: DINT → DINT, REAL → REAL, BOOL → BOOL
TIME tags publish as T#... duration strings on MQTT

Next Steps

EtherNet/IP Route

Explicit CIP Class/Instance/Attribute addressing for assembly objects and legacy devices.

Industrial Routes Overview

Compare OT routes and choose the right protocol for your devices.

Quick Start

Developing and Managing Coreflux

Coreflux MQTT Broker

LoT Language

Product Updates

Connect to Rockwell PLCs by Tag Name

Route and config aliases

Key capabilities

Quick Start

Connection Configuration

ALLEN_BRADLEY_CONFIG Parameters

Device Family Codes

Connection Examples

Tag Addressing

Tag naming rules

Data Types

STRING encoding

TIME encoding

TAG Configuration

Complete TAG Example

TAG Parameters

Publish Modes

Event-Based Operations

Query Parameters

Read Example

Write Example

Examples

Best Practices

Troubleshooting

Next Steps

EtherNet/IP Route

Industrial Routes Overview

​Connect to Rockwell PLCs by Tag Name

​Route and config aliases

​Key capabilities

​Quick Start

​Connection Configuration

​ALLEN_BRADLEY_CONFIG Parameters

​Device Family Codes

​Connection Examples

​Tag Addressing

​Tag naming rules

​Data Types

​STRING encoding

​TIME encoding

​TAG Configuration

​Complete TAG Example

​TAG Parameters

​Publish Modes

​Event-Based Operations

​Query Parameters

​Read Example

​Write Example

​Examples

​Best Practices

​Troubleshooting

​Next Steps

EtherNet/IP Route

Industrial Routes Overview

Connect to Rockwell PLCs by Tag Name

Route and config aliases

Key capabilities

Quick Start

Connection Configuration

ALLEN_BRADLEY_CONFIG Parameters

Device Family Codes

Connection Examples

Tag Addressing

Tag naming rules

Data Types

STRING encoding

TIME encoding

TAG Configuration

Complete TAG Example

TAG Parameters

Publish Modes

Event-Based Operations

Query Parameters

Read Example

Write Example

Examples

Best Practices

Troubleshooting

Next Steps