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VISA Overview

What Is VISA?

Virtual Instrument Standard Architecture (VISA) is a standard defined by Agilent Technologies® and National Instruments® for communicating with instruments regardless of the interface.

The Instrument Control Toolbox™ software supports the GPIB, VXI, GPIB-VXI, TCP/IP using VXI-11, TCP/IP using HiSLIP, USB, RSIB, and serial port interfaces using the VISA standard. Communication is established through a VISA instrument object, which you create in the MATLAB® workspace. For example, a VISA-GPIB object allows you to use the VISA standard to communicate with an instrument that possesses a GPIB interface.

    Note   Most features associated with VISA instrument objects are identical to the features associated with GPIB and serial port objects. Therefore, this chapter presents only interface-specific functions and properties. For example, register-based communication is discussed for VISA-VXI objects, but message-based communication is not discussed as this topic is covered elsewhere in this guide.

Interfaces Used with VISA

For many VISA applications, you can communicate with your instrument without detailed knowledge of how the interface works. In this case, you might want to begin with one of these topics:

If you want a high-level description of all the steps you are likely to take when communicating with your instrument, refer to the Getting Started documentation, linked to at the top of the Instrument Control Toolbox Doc Center page.

Supported Vendor and Resource Names

When you use instrhwinfo to find commands to configure the interface objects, you must use valid vendor or resource names. The supported values for vendor are given below.

Vendor

Description

agilent

Agilent Technologies VISA

ni

National Instruments VISA

tek

Tektronix® VISA (see note below for 64-bit support)

    Note:   For 64-bit Tektronix VISA support, it is important to note the following if you have a multi-vendor VISA installation (e.g., you have installed drivers from Tektronix and another vendor such as Agilent®). If you are using 64-bit Tektronix VISA on a machine with VISA implementations from multiple vendors, it is required that Tektronix VISA be configured as the primary VISA for it to be usable with Instrument Control Toolbox. Most 64-bit VISA implementations include a utility that allows you to select the primary and preferred VISA implementations. Use the VISA utility to set Tektronix VISA to be the primary VISA implementation on your machine. This step can be accomplished at any time, regardless of the order of installation of the VISA drivers.

The format for rsrc name is given below for the supported VISA interfaces. The values indicated by brackets are optional. You can use the instrument's VISA Alias for rsrcname.

Interface

Resource Name

GPIB

GPIB[board]::primary_address[::secondary_address]::INSTR

GPIB-VXI

GPIB-VXI[chassis]::VXI_logical_address::INSTR

RSIB

RSIB::remote_host::INSTR (provided by NI VISA only)

Serial

ASRL[port_number]::INSTR

TCPIP (VXI-11)

TCPIP[board]::remote_host[::inst0]::INSTR

TCPIP (HiSLIP)

TCPIP[board]::remote_host[::hislip0]::INSTR

USB

USB[board]::manid::model_code::serial_No[::interface_No]::INSTR

VXI

VXI[chassis]::VXI_logical_address::INSTR

The rsrcname parameters are described below.

Parameter

Description

board

Board index (optional — defaults to 0)

chassis

VXI chassis index (optional — defaults to 0)

interface_No

USB interface

lan_device_name

Local Area Network (LAN) device name (optional — defaults to inst0)

manid

Manufacturer ID of the USB instrument

model_code

Model code for the USB instrument

port_number

Serial port number (optional — defaults to 1)

primary_address

Primary address of the GPIB instrument

remote_host

Host name or IP address of the instrument

secondary_address

Secondary address of the GPIB instrument (optional — defaults to 0)

serial_No

Index of the instrument on the USB hub

VXI_logical_address

Logical address of the VXI instrument

obj = visa('vendor','rsrcname','PropertyName',PropertyValue,...) creates the VISA object with the specified property names and property values. If an invalid property name or property value is specified, an error is returned and the VISA object is not created.

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