NI-FBUS Basic Device option no longer available for Visitor address

[tew]

In version 3.2.1 of NI-FBUS Communications Manager it is possible to configure to use Device Address = Visitor and Device Type = Basic Device (in the NI-FBUS Interface Configuration Utility). This combination is useful when connecting to a segment already controlled by a host system (acting as LAS).

In version 4.x of NI-FBUS Communications Manager the combination Visitor and Basic Device is no longer available. You can only select Visitor + LAS.

Why is this combination no longer available? Is it always OK to use Visitor + LAS when there is already a different LAS on the segment?

Thanks!

[Really_Two]

Hi, I can explain something to you.

I have consulted our development team the reason why they do this change from NI-FBUS 4.0.

Foundation Fieldbus protocol specification says: "Visitor addresses are node addresses reserved for use by devices that are not normally continuously present on the network. They are used in FF networks by temporary devices such as hand-held terminals, configuration tools or diagnostic equipment."(FF-880, Chaptor 4, Page 9)

"A temporary device first listens to determine if there is any network traffic. If there is no traffic, it selects a visitor address and joins the network as the LAS." (FF-880, Chaptor 5, Page 12)

According to this explanation, the visitor device must have the capability to play as link master. However, basic device cannot support this feature. So we disabled this usage from NI-FBUS 4.0.

If you don't mind it is a basic device or a temporary master (don't worry it will cause some conflict with the current link master), please configure this interface device as Link Master with Visitor Address.

If there is some explicit reason, we will think about support it back in the following release.

[tew]

Thanks for the quick response!

So, just to confirm, if there is network traffic, then NI-FBUS will act as a basic device (not LAS) when using visitor address and not conflict with the current link master. Correct?

Also, does it work the same way for NI-FBUS 3.x? Can you configure Visitor + LAS for that version too with the same result as in 4.x?

The reason for asking is to make sure conflicts with the current Link Master on the network are avoided.

[Really_Two]

Yes, you are right.

NI-FBUS interface will not play as LAS but an FF device with master caplibility when it is in a visitor address. It should not conflict with the current LAS device.

Same as the basic+visitor usage in 3.2.X, using link master+visitor in 4.0.X can also help you connect to a segment already controlled by a host system (acting as LAS).

Thanks.

[tew]

We have users running either 3.x or 4.x. Can we configure Visitor+LAS for both versions with the same result? Or, do we need to use Visitor+Basic for 3.x and Visitor+LAS for 4.x?

Thanks again 🙂

[Really_Two · Accepted solution]

Yes. No matter 3.0 or 4.0,  the results are the same for vistor+LinkMaster configuration.

For any problems, you can contact us by fieldbus.support@ni.com.

Thanks.

[tew]

Thank you very much for all your help!