Modbus RTU is a serial communication protocol supported in EasyBuilder Pro that allows an HMI to communicate with PLCs and other devices over serial interfaces such as RS-232 or RS-485. It is a widely used protocol in industrial automation for exchanging data between devices when Ethernet is not required or available.
In EasyBuilder Pro, Modbus RTU is configured through the device settings by selecting the appropriate Modbus RTU driver and defining the communication parameters, such as baud rate, parity, and station address. The HMI typically acts as a client (master), sending requests to one or more Modbus RTU server (slave) devices on the serial network.
Communication is based on standard Modbus addressing, allowing the HMI to read and write different types of data:
- Coils and discrete inputs for bit-level data
- Registers for word-level data (read/write or read-only depending on type)
From the Maple Systems perspective, Modbus RTU is a core supported protocol that enables HMIs to integrate with a wide range of serial-based devices. It is especially useful in systems where multiple devices are connected on a shared RS-485 network using unique node addresses.
In practice, Modbus RTU is used to:
- Communicate with PLCs and field devices over serial networks
- Read process data into the HMI and write control values back to devices
- Integrate equipment from different manufacturers using a standard protocol
Overall, Modbus RTU provides a reliable and widely supported method for serial communication, making it a common choice for connecting HMIs to controllers and field devices in industrial systems.
Implementation of MODBUS RTU
There is no single “MODBUS RTU PLC”. Instead, there are hundreds! MODBUS, being an industry-standard communication protocol, is prevalent in many PLCs and other industrial devices. The beauty of this is that the device doesn’t need to have a proprietary communication and control system; using MODBUS RTU allows for serial communication to an incredibly wide variety of devices.