Configuring a Generic Modbus Controller

For each Generic Modbus controller on your system, you need to specify the controller features using the fields on the appropriate Generic Modbus Outstation Form. When configuring the database, select the type(s) of controller and communications that correspond to your system hardware.

The types of controller that the Advanced Modbus driver supports are listed below. For further information on the type(s) of controller that best represent your system set-up, see Outstation Types and Communications Set-ups.

The Advanced Modbus driver supports these types of controller (outstation):

• Generic Modbus Direct Outstation—Controllers that are directly connected to the Geo SCADA Expert server.

  Depending on the system set-up, a Direct controller can belong to a Direct or Switched Outstation Set.

• Generic Modbus PSTN Outstation—Controllers that communicate with the server using a dial-up modem.
• Generic Modbus Shared Outstation—Controllers that are directly connected to the Geo SCADA Expert server. A Shared controller can communicate with the server using either of two channels. Each controller in a Shared Set can communicate via either channel.

If your database structure is ‘modular’ and Group Templates are used to store ‘model’ Advanced Modbus configuration, in addition to the above types of controller, you can add driver-specific ‘abstract’ controller items to your Group Templates:

• Generic Modbus Abstract Outstation—Converts to any of the Generic Modbus Outstation items listed above.

You can only add Abstract Items to Group Templates. The abstract items appear as additional driver-specific entries when you display the context sensitive menu from a Group Template. As with other abstract items, in order to represent a ‘real’ controller, you need to convert the abstract items into the required type of controller (outstation) within the Group Instances that reference the Group Template. For more information, see Add an Abstract Item to a Group Template.

For each Generic Modbus controller on your system, you specify the controller features using the fields on the appropriate Generic Modbus Outstation Form. Each Form has several tabs.

Use the Modbus tab to:

• Specify the Controller Address
• Specify the Point Address Range
• Specify Whether the Registers are Swapped
• Specify when a Control Request has Completed Successfully
• Specify the Register Write Function
• Specify 32 Bit Register Compatibility
• Define the Data Retrieval Intervals
• Specify how any Scanning Gaps are Handled
• Specify any Local Pre and Post Amble Message Settings (see Define any Pre- and Post-Ambles for an Individual Outstation).

Use the Direct tab to:

• Specify whether a controller is given scanning preference while its Points are on display (see Define Whether an Outstation is Promoted While its Points are on Display)
• Specify the type of Direct Communications Connection (see Specify Whether the Direct Communications Connection is Always Online or only Available on Demand).

Use the PSTN tab to define the Public Switched Telephone Network properties for a controller (see Define an Outstation’s PSTN Properties.)

Use the Network tab to define additional properties for any network connected controller (see Define an Outstation’s Network Properties). (Port number 502 is the Modbus TCP port that is registered for use with the IANA (Internet Assigned Numbers Authority).)

Use the Shared tab to:

• Define when a Shared controller switches channels (see Define an Outstation’s Shared Properties).
• Additionally, if the controller is to use Heartbeat Polling, you need to Specify the Heartbeat Address that is used on a Shared Controller.

The fields on other tabs are common to controllers and outstations on many advanced drivers (see Tabs on Outstation Forms).

For information on the minimal amount of configuration that you can undertake to produce a functional Generic Modbus controller in Geo SCADA Expert, Minimum Configuration.