Connect to a Modbus device and map register addresses to tags.

Home → Tutorials → Industrial Operations Tutorial → Devices Module Tutorial → Connect to a Modbus Device Tutorial

This tutorial teaches you to:

  • Configure a Modbus TCP communication channel
  • Add a device node for a Modbus slave
  • Map Modbus register addresses to UNS tags
  • Monitor communication status at runtime

Prerequisites

1. Create the Device Channel

  1. Navigate to Devices → Channels
  2. Click New channel and configure:
    • Channel Name: ModbusChannel
    • Protocol: Modbus
    • Interface: TCP/IP

2. Add a Device Node

  1. Go to Devices → Nodes
  2. Create a node with:
    • Name: PLC1
    • Channel: ModbusChannel
    • PrimaryStation: 127.0.0.1;502;1 (semicolon-separated IP;Port;SlaveID — 502 is the standard Modbus TCP port, 1 is the unit/slave ID)

3. Create Device Points

Modbus addresses are composed as an operand prefix + a 5-digit zero-padded address. The operand selects the register family:

  • 0xxxxx — Coil (read/write bit)
  • 1xxxxx — Discrete Input (read-only bit)
  • 3xxxxx — Input Register (read-only 16-bit)
  • 4xxxxx — Holding Register (read/write 16-bit)
  1. Navigate to Devices → Points
  2. Add the points below.

Holding Register — Tank 1 Level:

  • Tag Name: TankFarm/Tank1/Level
  • Node: PLC1
  • Address: 400001 (Holding Register #1)
  • Data Type: Native
  • AccessType: ReadWrite

Holding Register — Tank 2 Level:

  • Tag Name: TankFarm/Tank2/Level
  • Node: PLC1
  • Address: 400002 (Holding Register #2)
  • Data Type: Native
  • AccessType: ReadWrite

Tip: Native lets the driver pick the data type from the register width. To force a specific type, use the canonical enum values (Real, Single, Bit, etc.) — see the Modbus driver Reference for the full list and for byte/word-order options.

4. Start the Modbus Device Simulator

  1. Navigate to Devices → Channels
  2. Select ModbusChannel
  3. Run the built-in Modbus Simulator (right-click the channel row → Run Simulator). The simulator listens on 127.0.0.1:502 by default and emulates a Modbus slave so you can test the loop without hardware.

5. Test Communication

  1. Click Start Runtime.
  2. Open Devices → Monitor.
  3. Confirm the node is healthy: ActivityCounter is increasing and LastErrorCode stays at 0.
  4. Open the tag-value view (Unified Namespace → Tags, runtime grid) and confirm TankFarm/Tank1/Level and TankFarm/Tank2/Level are receiving non-stale values from the simulator.