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Chapter 1 Overview of NI-VXI
© National Instruments Corporation 1-3 NI-VXI User Manual
Message-Based Devices
In addition to register-based devices, the VXIbus specification also
defines message-based devices, which are required to have
communication registers in addition to configuration registers. All
message-based VXIbus devices, regardless of the manufacturer, can
communicate at a minimum level using the VXI-specified Word Serial
Protocol. In addition, you can establish higher-performance
communication channels, such as shared-memory channels, to take
advantage of the VXIbus bandwidth capabilities.
Device-
Specific
Protocols
Device-
Specific
Protocols
Shared-
Memory
Protocol
488-VXIbus
Protocol
Device-
Specific
Protocols
488.2
Syntax
Word Serial Protocol
Communication Registers
Configuration Registers
Device-
Specific
Protocols
Figure 1-2. VXI Software Protocols
Word Serial Protocol
The VXIbus Word Serial Protocol is a standardized message-passing
protocol. This protocol is functionally very similar to the IEEE 488
protocol, which transfers data messages to and from devices one byte
(or word) at a time. Thus, VXI message-based devices communicate in