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Chapter 3 Configuration and Installation
© National Instruments Corporation 3-31 VXI-MXI User Manual
Keep in mind that a system can contain only one device acting as the VXIbus Resource Manager
(RM). It is important that the RM be run only after all other devices in the system have been
powered on. Because many RMs execute automatically upon power-up, you must be sure when
working with a distributed system to power-on the device containing the RM last. This implies
that any VXI-MXIs in that frame must be the MXIbus System Controllers for their respective
MXIbus systems to keep the preceding power-on procedures for individual MXIbus systems.
VMEbus Devices in VXIbus/MXIbus Systems
If you have VMEbus devices installed in your VXIbus system, pay special attention to how the
A16 resources used by the VMEbus cards are configured. The VXIbus specification has
reserved the upper 16 KB of A16 space for configuration registers on VXIbus devices. During
system initialization, the system Resource Manager scans the upper 16 KB of A16 searching for
VXIbus devices. Ensure that VMEbus devices are not mistaken for VXIbus devices.
If possible, you should configure the A16 resources for your VMEbus boards in the lower 48 KB
(0000 through BFFF hex) of A16 space, so as to not interfere with VXIbus configuration space.
The logical address window is then used for mapping configuration space for VXIbus devices,
while the A16 window is used for mapping configuration space for VMEbus devices. If you
must configure any of the VMEbus module's A16 resources in the upper 16 KB (C000 through
FFFF hex) of A16 space, you need to indicate to the system Resource Manager that there are
non-VXIbus foreign devices installed. Be careful not to configure any static VXIbus logical
addresses in the portions of A16 space occupied by the VMEbus devices.