National Instruments VXI-USB User Manual

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© National Instruments Corporation
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Common Questions
This appendix addresses common questions you may have about using the 
NI-VISA/NI-VXI software on the VXI-USB platform.
What does hot plugging mean in terms of USB?
The concept of hot plugging in USB means that you can remove and insert 
USB cables without powering down your computer and devices. The USB 
Plug and Play architecture is designed so that the host computer can 
recognize when to load and remove the appropriate drivers.
Does it matter if I plug my VXI-USB or other USB device into any 
particular USB port? For example, does it matter whether I plug a 
USB device into the USB ports in my computer or into the VXI-USB in 
my mainframe?
A USB device may be plugged into any port on the VXI-USB or your 
computer. Doing so can change the topology of the system, which may 
affect system performance in some cases. The effect may vary greatly, 
depending on the system and types of devices installed.
Also, if your computer has integrated USB 2.0, you should use one of the 
integrated ports rather than a USB 2.0 plug-in card if possible. Integrated 
USB 2.0 ports typically offer better performance due to their tight coupling 
with your motherboard and chipset. Of course, if you have the choice 
between a USB 2.0 port and a USB 1.x port, always use the USB 2.0 port 
even if that means you are using a plug-in card instead of an integrated port.
I need more devices than can fit in one chassis. How can I expand my 
VXI-USB system?
You can add another VXI-USB to the system, but the additional chassis will 
not share the same VXI bus. The recommended strategy is to use a 
VXI-MXI-2, which follows the VXI-6 specification for mainframe 
extension. This extends full VXI functionality across multiple mainframes, 
including a common device address space and interframe triggering, 
interrupts, and bus mastering. Place a VXI-MXI-2 in the same frame as the 
Slot 0 VXI-USB, and another VXI-MXI-2 in Slot 0 of the next mainframe. 
You can then fill up this mainframe with additional devices.