DSC I/O Group Update Rate

[stephen s]

I am editing my DSC tag configuration using the Tag Editor, and want to change the Update rate {Connection»I/O Group»Edit Default Parameters»Update Rate (secs)} to a smaller value (~0.05 sec). However, I cannot change this value with the editor. When I change it and click OK, the value has reset to 0.2 when I revisit it.

Am I changing it correctly? Do I just have to change it once, or must I do this for every tag? I cannot see a place in the individual tag configuration to edit update rate.

[Jochen]

If you change the default parameters these values are not updated for existing tags but these will be the default parameters for new tags.

The update period is a parameter that is passed to the server you are using. You can define various I/O groups with different update rates. If you want to change the server update rate for your tags you only have to do this for each I/O group you have configured. If you have only configured one I/O group you only have to do this once in the configuration of any tag you like.

Just to clarify this: The I/O group update period is just a parameter that is passed to the (OPC-) server DSC is talking to. That means if your server communicates with your field devices through polling then this parameter should define the poll rat
e of your server. The data communication from the LV DSC engine to the HMI application and to the database is still event driven. The update rate of these communication processes is not constant but defined by the rate of change of your monitored signals and by the update deadband you have defined in the Tag Configuration Editor.

There is a very good document in the NI developer zone about these issues:
http://zone.ni.com/devzone/conceptd.nsf/webmain/E6A1F57863E8D7E686256A140050A90B?opendocument

Best regards,

Jochen Klier
NI-Germany