On a Geo SCADA Expert system, you configure the Geo SCADA Expert database so that entries in the database correspond to the devices on your system. This section summarizes the database items that you need to configure to represent the Modbus Slave devices on your system.
To function as a Modbus Slave, the Modbus Slave Driver has to be installed and running on the Geo SCADA Expert servers on your system. The Modbus Slave driver allows Geo SCADA Expert to act as a Modbus PLC, and use the Modbus protocol to talk to a Modbus Master (for example, another server). The driver is represented by the Modbus RTU Slave component in the Geo SCADA Expert Installation Wizard’s Setup window. The component is located within the Server branch of the tree that is displayed in the window (see Install a Driver in Geo SCADA Expert in the Geo SCADA Expert Guide to Drivers).
When you configure Modbus Slave items in the Geo SCADA Expert database, many of the properties for those items need to correspond to the properties of the relevant Modbus Master on your system. Some properties are either fixed (incorporated into the design of the Modbus Master), or are configured by an engineer. You need to have access to, or an understanding of, the properties of the Modbus Master on your system before you can configure the Modbus Slave database items successfully.
For example, you need to know the type(s) of communications available for the Modbus channels on your system, and how those communications are structured or grouped.
You also need to be aware of which optional features are required for each Modbus Slave item. These features include:
- Alarm views
- Alarm redirections
- User methods.
You can also use core Geo SCADA Expert features with Modbus Slave database items, including Lists, Actions, and Mimics. See the core documentation for details.
For each Modbus Slave device, you need to configure:
- Modbus Slave Channel(s) to represent the communication connections between the Slave and its Master (see Configuring a Modbus Slave Channel).
- Value Map(s) for mapping ‘point’ properties into memory so that they can be accessed by the Slave’s Master (see Using Value Maps to Represent Modbus Data Address Ranges, and see Configuring Value Maps in the Geo SCADA Expert Guide to Core Configuration).
- Modbus Slave Source(s) to specify which Value Maps—blocks of data—are to be scanned by a particular Master device (see Configure the Basic Source Properties). Configure a separate Source for each block of data that is to be scanned separately to other data, for example, by a different Master scanner.
To minimize the time that it takes to configure the required Modbus Slave items, you may want to configure them in the order listed above, as, for example, Source configuration requires you to specify a channel and the Value Maps that hold the Source’s ‘point’ data.