Modbus in Ignition SCADA — Configuring Modbus TCP and RTU Drivers
Key Takeaway
How to configure Modbus TCP and RTU device connections in Ignition SCADA — driver setup, tag addressing, data types, byte order, and troubleshooting.
Quick Answer
Ignition's built-in Modbus driver supports Modbus TCP and RTU (serial or serial-over-TCP). Tags use the HR (holding register), IR (input register), C (coil), and D (discrete input) prefix convention.
Creating a Modbus TCP Connection
- Gateway → Config → OPC-UA → Devices → New Device
- Select Modbus TCP
- Enter IP address and port 502
- Set Unit ID and timeout
Tag Addressing
- HR1 — Holding register 40001
- IR1 — Input register 30001
- C1 — Coil 00001
- D1 — Discrete input 10001
Data Types
Int2 (16-bit), UInt2, Int4 (32-bit), Float4 (32-bit IEEE 754), Float8 (64-bit double). Select per tag.
Byte Order
Big-Endian, Little-Endian, Big-Endian Byte Swap, Little-Endian Byte Swap. Match to device manufacturer documentation. See byte order guide.
Examples
Reading ABB Totalflow flow data and IDEC FC6A analog values via Modbus TCP in Ignition.
Troubleshooting
Bad_NotConnected: verify IP and port. Bad_Stale: check register address. Wrong value: check byte order.
Frequently Asked Questions
HR prefix for holding registers (HR1 = 40001), IR for input registers, C for coils, D for discrete inputs.
In the tag's Modbus settings, select Float4 data type and choose Big-Endian, Little-Endian, or byte-swapped variants to match the device.