Modbus Client and Server Configuration in SEL RTAC
Key Takeaway
How to configure Modbus TCP and RTU client and server drivers in the RTAC — register mapping, data types, byte order, and integration with meters and SCADA.
Quick Answer
The RTAC supports simultaneous Modbus TCP client (polling meters), Modbus RTU client (polling serial devices), Modbus TCP server (serving data to legacy SCADA), and Modbus RTU server — all running concurrently.
Modbus Client
Poll power meters, VFDs, and other Modbus devices. Configure target IP/port (TCP) or serial port/baud (RTU), register addresses, data types (UINT16, INT32, REAL32), and byte order. See Modbus function codes for register access details.
Modbus Server
Expose RTAC tag data as Modbus registers for legacy SCADA or energy management systems. Define register map linking RTAC tags to Modbus addresses.
Use Cases
- Poll Schneider PM power meters via Modbus TCP
- Poll VFDs via Modbus RTU
- Serve substation data to legacy Modbus-only SCADA
Frequently Asked Questions
Yes. Multiple Modbus client and server drivers run concurrently in the same project.
Per tag in the driver settings — Big-Endian (ABCD), Little-Endian (DCBA), or byte-swapped variants. Match the source device manufacturer's documentation.