Modbus is a communications protocol for Programmable Logic Controllers (PLCs) openly published by Modicon (now part of Schneider Electric). Since its publication in 1979 Modbus has been widely adopted as a communications protocol for PLCs.
The Fernhill SCADA Modbus driver scans PLCs (or other types of device) for data using the Modbus communications protocol. The Modbus driver supports these variants of the Modbus protocol:
| Protocol | Description |
|---|---|
| Modbus RTU | 8-bit serial binary protocol |
| Modbus ASCII | 7 bit serial ASCII protocol |
| Modbus TCP | TCP/IP protocol |
| Modbus RTU over TCP | Modbus RTU over TCP/IP |
The Modbus driver provides these tag types to support communication using the Modbus protocol:
| Icon | Tag Type | Version | Description |
|---|---|---|---|
|
Modbus TCP Channel Tag | 1.0 | A connection to a Modbus device using the TCP/IP protocol. |
|
Modbus Serial Channel Tag | 1.0 | A serial port used for Modbus serial communications. |
|
Modbus Device | 1.0 | A device supporting the Modbus protocol. |
|
Modbus Register Block Tag | 1.0 | A block of registers read from modbus device. |
The Modbus tags you configure tells the driver how to interact with Modbus PLCs.
The Serial Device Configuration Walkthrough provides step by step instructions on configuring tags manually.
You can use these I/O Data Point Tags to represent individual data points in the PLC:
| Icon | Tag Type | Version | Description |
|---|---|---|---|
 |
I/O Analog Data Point Tag | 3.12 | Maps an Analog Data Point Tag to an external data source. |
 |
I/O Digital Data Point Tag | 3.12 | Maps a Digital Data Point Tag to an external data source. |
 |
I/O Word Data Point Tag | 3.12 | Maps a 16-bit Word Data Point Tag to an external data source. |
 |
I/O Double Word Data Point Tag | 3.12 | Maps a 32-bit Double Word Data Point Tag to an external data source. |
 |
I/O Long Word Data Point Tag | 3.48 | Maps a 64-bit Long Word Data Point Tag to an external data source. |
The Modbus driver supports these Autodetect Wizards:
| Wizard | Description |
|---|---|
| Modbus Serial | Searches serial ports for PLCs supporting the Modbus protocol. Supports both RTU and ASCII variants. |
| Modbus TCP | Searches an Ethernet network for PLCs supporting the Modbus TCP protocol. |
For a description of the Modbus Protocol.
For a description of how Modbus data addressing works in Fernhill SCADA.
Modbus Serial Autodetect Wizard
To learn about the Modbus Serial autodetect wizard.
To learn about the Modbus TCP autodetect wizard.
For background information on serial communications.
For information about other drivers available in Fernhill SCADA.
For the meaning of terms used in Fernhill SCADA.