Chapter 2
Hardware Configuration and Installation
© National Instruments Corporation
2-11
VXI-SB2020 and NI-VXI for Solaris
VMEbus Request Level Selection
The VXI-MXI uses one of the four VMEbus request levels to request use of the VME Data
Transfer Bus (DTB). The VXI-MXI requests use of the DTB whenever an external MXIbus
device, such as a Sun workstation with an SB-MXI interface, attempts a transfer that maps into
the VXIbus mainframe.
The VXI-MXI uses VMEbus request level 3 in its factory default setting, as required by the
VXIbus specification. This is suitable for most VXIbus systems. However, you can change the
VXI-MXI to use any of the other three request levels (0, 1, or 2) by changing the jumper
configuration on the jumper blocks labeled VMEbus Request Level on the front panel. You may
want to change request levels to change the priority of the VXI-MXI request signal. For more
information, refer to the VMEbus specification.
To change the VMEbus request level of the VXI-MXI, rearrange the jumpers on the pin arrays as
shown in Figure 2-7.
a. Level 3 Requester (default)
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VMEbus Request Level
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b. Level 2 Requester
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c. Level 1 Requester
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d. Level 0 Requester
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Figure 2-7. VXI-MXI VMEbus Requester Jumper Settings
