multiple hosts

[tim58]

Are there any incompatibilities in various vendors FFBUS products? I have an application for a standalone Windows 2000 based PC system and was planning on using the PCI-FBUS/2 card to communicate from this PC to a larger DCS system that controls the facility where this device will be installed. The DCS support people have a concern about using the NI FBUS/2 card. They indicate that it is configured to operate as a "host" which will cause problems on their system. (Sorry I don't have information on their system right now) It was my understanding that as long as the device is labelled as Foundation Fieldbus device, it should work. It is also my understanding that it is normal for multiple "hosts" to be on the same network. Please advise.


Also, from what I understand about FFbus, I can communicate multiple pieces of data from the PC to the DCS and vice versa. It is basically a network connection connection between the 2 machines. Please advise on this as well.

Thanks for your support.

[fieldbus]

I guess the concern from DSC support people is related to LAS (Link Active Scheduler) conflict. As you know, the LAS is the master device to manage the fieldbus communications, and there should be only one LAS present in one fieldbus link (segment). If there are multiple devices trying to take the role as LAS, the bus communications would fail with conflict. In this case, the concern is reasonable because the PCI-FBUS/2 might start as LAS device to conflict with DSC H1 interface, which used to be LAS device for a system.

However, you can simply change some settings of PCI-FBUS/2 to avoid such conflict. Please follow the steps below:
1. Make sure the NI-FBUS Communications Manager (CM) and Configurator software are not started;
2. Run the Interface Configuration Utility;
3. Click the ports of the PCI-FBUS board like "Port0" and "Port1", click "Edit", then "H1 Port Properties" dialog appears;
4. Set the "Device Address" to "visitor", set the "Device Type" to "Basic Device", and the "Usage" as "NI-FBUS";
5. Click OK, close the Interface Configuration Utility;
6. Connect the PCI-FBUS/2 port to fieldbus segment (having DSC connected);
7. Start NI-FBUS CM or NI-FBUS Configurator software;

After that, you can run PCI-FBUS/2 together with the DSC system without conflict. The settings of "Visitor" configures the PCI-FBUS in Visitor address, so it would not have address conflict with DSC H1 interface; the settings of "Basic Device" configures the PCI-FBUS running as Basic Device which has no capability to take the role of LAS.

Hope it helps.