National Instruments MXI-2 Series Getting Started page 60

Glossary
VMEbus System
Controller
VXIbus
W
Word Serial Protocol
write posting
PCI-Based MXI-2 Interface for Windows
A device configured for installation in Slot 0 of a VXIbus mainframe or
Slot 1 of a VMEbus chassis. This device is unique in the VMEbus system
in that it performs the VMEbus System Controller functions, including
clock sourcing and arbitration for data transfers across the backplane.
Installing such a device into any other slot can damage the device, the
VMEbus/VXIbus backplane, or both.
VMEbus eXtensions for Instrumentation
The simplest required communication protocol supported by
message-based devices in a VXIbus system. It utilizes the A16
communication registers to transfer data using a simple polling handshake
method.
A mechanism that signifies that a device will immediately give a successful
acknowledge to a write transfer and place the transfer in a local buffer. The
device can then independently complete the write cycle to the destination.
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