Multiple NI PCI GPIB Controllers programming

[Josecho]

I am aware of the GPIB limitations (less that ~ 12 devices and less than 20 meter cable length). I have decided to have two NI PCI GPIB controller cards. I will have 8 devices connected to first NI PCI GPIB card (GPIB address 0) and 7 devices to the second NI PCI GPIB card (GPIB address 1). I have one computer with two NI PCI GPIB cards both configured as controller,basically two separate GPIB bus. My question is when I use the Labview GPIB reads and writes function there is no specification for which boards it is controlling, are both cards actually sending the GPIB reads and writes? I am assuming that since all devices have a unique address, only the device addressed will respond and therefore there is not bus conflict. Is there going to be a Bus Error (Timeout No Listener) on the controller that did not get a response?

[Dennis_Knutson]

There is a specification for which bus you're communicating over and you have to use it. Otherwise, all commands will go out over the first card. Also, with two cards, you only have to have unique addresses on each bus. For VISA, which I recomend you use, the resource name takes the form of GPIBx::ADDDR:INSTR so you would GPIB0:: for instruments connected to the first boards and GPIB1:: for instruments to the second. VISA is really a lot easier because you can just select from a list of available instruments. For traditional GPIB, to quote the on-line help "When there are multiple GPIB Controllers that LabVIEW can use, a prefix to address string in the form ID:address (or ID: if no address is necessary) determines the Controller that a specific function uses. If a Controller ID is not present, the functions assume Controller (or bus) 0."