Additional Programming Issues

For advanced users, the GPIB-VXI Mainframe Backplane resource encapsulates the operations and properties of each mainframe (or chassis) in a VXIbus system. This resource type lets a controller query and manipulate specific lines on a specific mainframe in a given VXI system. The form of the resource string for this class is "GPIB-VXI<system>::BACKPLANE". Services in this resource class allow the user to map, unmap, and assert hardware triggers, and also to assert various utility signals.

Although the VISA API is almost identical for VXI and GPIB-VXI, the GPIB-VXI implements only a subset of this functionality. As mentioned above, the GPIB-VXI does not support 32-bit register accesses, nor does it support A32 space. The attributes VI_ATTR_SRC_ACCESS_PRIV, VI_ATTR_DEST_ACCESS_PRIV, and VI_ATTR_WIN_ACCESS_PRIV can only be set to the value VI_DATA_PRIV; other address modifiers are not supported. The attributes VI_ATTR_SRC_BYTE_ORDER, VI_ATTR_DEST_BYTE_ORDER, and VI_ATTR_WIN_BYTE_ORDER can only be set to the value VI_BIG_ENDIAN; little endian transfers are not supported. Also, while the GPIB-VXI does support service request events, it does not support receiving the following events: miscellaneous VXI signals or interrupts, triggers, SYSFAIL, or SYSRESET.

If you have more than one GPIB-VXI controller in your system, or if you change the primary address of a GPIB-VXI controller from its default (1 for the National Instruments GPIB-VXI/C), or if you have a GPIB-VXI controller from another vendor, then you need to configure NI-VISA to find such a controller. Use the NI-VISA configuration utility (MAX on Windows, visaconf on UNIX) and explicitly add a GPIB-VXI controller. You will be prompted for the GPIB controller number to which the GPIB-VXI is connected (usually 0), a unique GPIB-VXI controller number (which you are free to assign), and the primary and secondary addresses to which you have configured this GPIB-VXI controller.