FS-8700-01 – Modbus RTU
The Modbus RTU driver is a primary communication interface for the FieldServer, designed to facilitate high-speed data transfer between devices over serial interfaces. It enables industrial integration by utilizing either RS-232 or RS-485 physical layers.
Beyond simple data translation, the FieldServer can function as a port expander, allowing legacy serial equipment to be bridged into modern Building Automation Systems (BAS) or Industrial Control Systems.
Driver Capabilities and Emulation Modes
This serial driver supports both Client and Server emulation. It is technically robust, offering support for devices that utilize two consecutive Modbus registers to transfer 32-bit IEEE floating-point data formats.
Node Support and Loading:
| FieldServer Mode | Nodes | Technical Comments |
|---|---|---|
| Client | 1 | Only 1 client node is permitted on Multidrop systems. |
| Server | 255 | Electrical loading on the RS-485 bus may reduce the total number of usable server nodes. |
Hardware Connection and Serial Settings
To ensure reliable serial communication, the Modbus RTU driver requires specific hardware parameters. The RS-485 implementation is typically Two-wire, Half-Duplex.
- Baud Rates: Supports a wide range from 110 to 115200.
- Data Framing: 8 Data Bits, 1 Stop Bit, and None (No Parity).
- Multidrop: Fully capable of multidrop installations over RS-485.
Compatibility Matrix and Tested Devices
The Modbus RTU driver is verified for use with modern FieldServer hardware, including the FS-x20, FS-x30, and FS-x40 series. It has undergone extensive testing with a variety of third-party controllers and software packages.
| Device / Software | Testing Environment |
|---|---|
| Liebert Sitelink | Customer Site |
| WonderWare InTouch / Fix Intellution | Factory Tested |
| Sierra Monitor Sentry | Factory Tested |
| GE Cimplicity / ABB Extrel | Customer Site |
| Andover Controls / Square D | Customer Site |
Supported Modbus Function Codes
The driver implements standard Modbus function codes for managing discrete and register data:
- 01 & 02: Read Discrete Output Status (0xxxx) and Input Status (1xxxx).
- 03 & 04: Read Output (Holding) Registers (4xxxx) and Input Registers (3xxxx).
- 05 & 06: Force Single Coil and Preset Single Register.
- 15 & 16: Force Multiple Coils and Preset Multiple Registers.
FAQ – Modbus RTU Integration
1) Can this driver handle 32-bit integers?
Yes. By combining two 16-bit Modbus registers, the driver can process both IEEE floating-point and 32-bit integer data formats.
2) What is the difference between RS-232 and RS-485 for Modbus?
RS-232 is typically used for point-to-point connections over short distances, while RS-485 supports multidrop networking with up to 255 server nodes.
3) Do I need a different driver for Modbus TCP?
Yes. Modbus RTU is for serial communications. If you are integrating over Ethernet, you will require the Modbus TCP driver, which Chipkin also provides.
Need a Complete Modbus Integration?
Chipkin offers expert-level tools including stacks, scanners, and diagnostic software to ensure your Modbus network operates at peak efficiency:
