National Instruments NI-VXI

Chapter 1 Overview of NI-VXI

such information via interrupts, whereas devices that do have bus

master capability can either use interrupts or send signals. Some

devices can receive only signals, some only interrupts, while some

others can receive both signals and interrupts.

The VXIbus specification defines Word Serial commands so that a

Commander can understand the capabilities of its Servants and

configure them to generate interrupts or signals in a particular way. For

example, a Commander can instruct its Servants to use a particular

interrupt line, to send signals rather than generate interrupts, or

configure the reporting of only certain status or error conditions.

Although the Word Serial Protocol is reserved for Commander/Servant

communications, you can establish peer-to-peer communication

between two VXI/VME devices through a specified shared-memory

protocol or simply by writing specific messages directly to the device’s

Signal register, in addition to the VXI/VME interrupt lines.

MXIbus Overview

The MXIbus is a high-performance communication link that

interconnects devices with a cabled communication link for very

high-speed communication between physically separate devices. The

emergence of the VXIbus inspired MXI. National Instruments, a

member of the VXIbus Consortium and the VITA organization,

recognized that VXI requires a new generation of connectivity for the

instrumentation systems. Additionally, National Instruments realized

that the same technology could be used also for the VMEbus, which is

the foundation technology under VXI. National Instruments developed

the MXIbus specification over a period of two years and announced it

in April 1989 as an open industry standard.

MXI-2 Overview

MXI-2 is the second generation of the National Instruments MXIbus

product line. The MXIbus is a general-purpose, 32-bit, multimaster

system bus on a cable. MXI-2 expands the number of signals on a

standard MXI cable by including VXI triggers, all VXI/VME

interrupts, CLK10, and all of the utility bus signals (SYSFAIL*,

SYSRESET*, and ACFAIL*).