Vmodbus Set-up

First Define the Overall System Parameters

If maintaining an existing system, first one opens the system configuration file. The overall system parameters can then be defined or modified: the retry parameters, the debug and watchdog parameters and the SHEF-A parameters (if needed)

Then Define the Computer Ports and the Poll Groups

Vriver supports three Modbus protocols over either serial or Ethernet ports. One system can be configured for multiple ports and communication protocols

As different registers and channels (tags) are likely to have different poll time requirements, these are defined in the upper part of this screen. Notice that one can optionally define the time that the polling will start, which is derived from the “Poll Every” field, the “Start poll at” field and the time that the system is started. In addition, if required, all values read in a poll group can have the same time stamp, that of the time for the start of that particular poll cycle. Thus, for example, the 30-minute poll can be set to be on the exact hour and half hour and every value read will have the same, exactly on the hour and half hour, time stamp, however long the poll cycle actually takes.

Finally Define the Stations on Each Port and the Channels

The upper part of this screen defines the stations on the ports. A Virtual Station is one that does not exist as connected to a Modbus port, and thus does not use a station ID, but is made to look like a Modbus Station to the rest of the Vsystem application and is used for calculated values.

The lower part of the screen is used to define the channels associated with each Modbus device. Once again, calculated values can be defined as virtual registers that are seen by the rest of the Vsystem application as RTU registers but are actually calculated values derived from scanned-in measurements.  Virtual registers can also be higher-level controls, implemented by the Vsystem application, and which result in changes to one or more device registers.

The Alarms & Log  tab helps you set the alarm and warning values, if needed, and the historian file in which to record these values. In addition, the whole application can be divided into areas and subareas where this is appropriate to help management of the system. 

Finally, the Advanced tab is used to set the parameters for linear conversion or, alternatively, the conversion routine. This conversion routine can either be a subroutine in a library or a typed-in equation that can access any other values in the system. Display parameters can be defined as well as the SHEF-A details for this value.

When all is done, it is just a matter of saving the configuration and running the automatically-generated start file and the system is running! All that then remains is to draw the required HMI screens.

Updated Jan 4, 2010.