Glossary
A string (or other language construct) that uniquely locates and identifies a resource. VISA defines an ASCII-based grammar that associates address strings with particular physical devices or interfaces and VISA resources.
See VISA alias.
Application Programming Interface. The interface that a programmer sees when creating an application. For example, the VISA API consists of the sum of all of the operations, attributes, and events of each of the VISA ResourceClasses.
In VISA and SICL, a value that indicates the operational state of a resource. Some attributes can be changed; others are read-only.
An error that signals failure to access an address. Bus errors occur in conjunction with low-level accesses to memory, and usually involve hardware with bus mapping capabilities. Bus errors may be caused by non-existent memory, a non-existent register, an incorrect device access, etc.
Software that runs when a bus error occurs.
In test-system architectures, a device that has the ability to control another device. In a specialized case, a commander may also be the device that has sole control over another device (as with the VXI Commander/Servant hierarchy).
A communication path between a software element and a resource. In VISA, "communication channel" is synonymous with "session". Every communication channel in VISA is unique.
An Agilent software utility that helps you quickly establish connections between your instruments and your PC. It also helps you troubleshoot connectivity problems. Connection Expert is part of the Agilent IO Libraries Suite product.
A device (typically a computer) used to communicate with another device or devices (typically instrument). The Controller is in charge of communications and device operation; it controls the flow of communication and performs addressing and other bus management functions.
A unit that receives commands from a Controller. A device is typically an instrument, but can also be a computer acting in a non-Controller role or another peripheral such as a printer or plotter. In VISA, a device is logically represented by the association of several VISA resources.
Software code that communicates with a device: for example, a printer driver that communicates with a printer from a PC. A device driver may either communicate directly with a device by reading to and writing from registers,or it may communicate through an interface driver.
A session that communicates as a Controller with a single, specific device such as an instrument.
See "instrument driver" and "device driver".
The tree view within the Connection Expert window that shows all devices connected to a test system.
A software routine that responds to an asynchronous event such as an SRQ or an interrupt.
HiSLIP (High Speed LAN Instrument Protocol) is a protocol for TCP-based instrument control that provides the instrument-like capabilities of conventional test and measurement protocols with minimal impact to performance.
A device that accepts commands and performs a test and measurement function.
Software that runs on a computer to allow an application to control a particular instrument.
An Agilent application that allows you to interactively send commands to instruments and read the results. Interactive IO is part of the Agilent IO Libraries Suite product.
A connection and medium of communication between devices and controllers. Interfaces include mechanical, electrical, and protocol connections.
Software that communicates with an interface. The interface driver also handles commands used to perform communications on an interface.
A session that communicates and controls parameters affecting an entire interface.
An asynchronous event that requires attention and actions that are out of the normal flow of control of a program.
The icon in the Windows notification area (usually the lower right corner of your screen). The IO Control gives you access to Agilent I/O utilities such as Connection Expert, Agilent I/O documentation, and VISA options.
Application programming interfaces (APIs) for direct I/O communication between applications and devices. There are four Agilent IO Libraries in the Agilent IO Libraries Suite: VISA, VISA COM, SICL, and Agilent 488.
A state that prohibits other users from accessing a resource such as a device or interface.
An operation that returns a reference to a specified section of an address space and makes the specified range of addresses accessible to the requester. This function is independent of memory allocation.
A computer is in a non-Controller role when it acts as a device communicating with a computer that is in a Controller role.
The area on the Windows taskbar where notifications are posted, typically in the lower right corner of the screen. Also called "taskbar notification area"or "Windows notification area".
A defined action that can be performed on a resource.
The VISA installation that controls the visa32.dll file. The primary VISA will be used by default in VISA applications. See also "secondary VISA".
An operating system component that shares a system's resources. A single-process computer system allows only a single program to execute at any given time. A multi-process computer system allows multiple programs to execute simultaneously, each in a separate process environment.
PXI is a rugged, high-performance modular instrumentation platform designed for industrial measurement and automation applications. PXI allows you to use modules from multiple vendors and easily integrate them into a PXI system.
Note: Programming is identical for PXI, PXIe and PCIe device types. The term PXI is used in this document to represent all three device types.
In Connection Expert, the action that invokes the discovery mechanism for detecting interfaces and instruments connected to your computer. The explorer view is then refreshed to show the current, discovered state of your test system.
An address location that contains a value that represents the state of hardware, or that can be written into to cause hardware to perform a specified action or to enter a specified state.
In VISA, an implementation of a resource class (in object-oriented terms, an instance of a resource class). For example, an instrument is represented by a resource instance.
The definition of a particular resource type (a class in object-oriented terms). For example, the VISA Instrument Control resource classes define how to create a resource to control a particular capability of a device.
A string, such as a VISA resource descriptor, that specifies the I/O address of a device.
Standard Commands for Programmable Instrumentation: a standard set of commands, defined by the SCPI Consortium, to control programmable test and measurement devices in instrumentation systems.
A VISA installation that does not install visa32.dll in the standard VISA location. A secondary VISA installation names its VISA DLL with a different name (such as agvisa32.dll) so that it can be accessed programmatically. The primary VISA will be used by default in VISA applications. See also "primary VISA".
VISA term for a communication channel. An instance of a communications path between a software element and a resource. Every communication channel in VISA is unique.
Standard Instrument Control Library. SICL is an Agilent-defined API for instrument I/O. Agilent SICL is one of the IO Libraries installed with Agilent IO Libraries Suite.
A side-by-side installation allows two vendors' implementations of VISA to be used on the same computer. See also "primary VISA" and "secondary VISA".
An IEEE-488 Service Request. This is an asynchronous request (an interrupt) from a remote device that requires service. In GPIB, an SRQ is implemented by asserting the SRQ line on the GPIB. In VXI, an SRQ is implemented by sending the Request for Service True event (REQT).
A byte of information returned from a remote device that shows the current state and status of the device. If the device follows IEEE-488 (GPIB) conventions, bit 6 of the status byte indicates whether the device is currently requesting service.
A name corresponding to a single interface. This name uniquely identifies the interface on this Controller or gateway. When there is more than one interface on the Controller or gateway, each interface must have a unique symbolic name.
The information and logic represented in the left pane of the ConnectionExpert window. The task guide provides links to actions and information that help guide you through the most common I/O configuration tasks.
See "notification area".
An entire test setup including a controller (often a PC), instruments, interfaces, software, and any remote controllers, instruments, and interfaces that are configured to be used as part of the system.
An operating system object that consists of a flow of control within a process. A single process may have multiple threads, each having access to the same data space within the process. Each thread has its own stack, and all threads may execute concurrently (either on multiple processors, or by time-sharing a single processor).
A console application that uses the viFindRsrc and viFindNext VISA functions to enumerate all resources visible to VISA. This application is useful for verifying that all expected interfaces have been configured by Connection Expert, and that the expected devices have been attached. ViFind32 is part of the Agilent IO Libraries Suite.
A name given to the grouping of software modules (such as VISA resources with any associated or required hardware) to give them the functionality of a traditional stand-alone instrument. Within VISA, a virtual instrument is the logical grouping of any of the VISA resources. The VISA Instrument Control Resources Organizer serves as a means to group any number of any type of VISA Instrument Control Resources within a VISA system.
Virtual Instrument Software Architecture. VISA is a standard I/O library that allows software from different vendors to run together on the same platform. Agilent VISA is part of the Agilent IO Libraries Suite.
A resource descriptor that can be used to open a VISA session.
A string that can be used instead of a resource descriptor in VISA programs. Using VISA aliases rather than hard-coded resource descriptors makes your programs more portable. You can define VISA aliases for your instruments in Connection Expert.
The VXIplug&play specification for a COM-compliant VISA I/O library and its implementation. Agilent VISA COM is part of the Agilent IO Libraries Suite.
The VISA definition of device-specific resource classes. VISA Instrument Control Resources include all VISA-defined device and interface capabilities for direct, low-level instrument control.
The prefix of a VISA address, also called the VISA interface ID. The VISA name specifies the interface.
The part of VISA that manages resources. This management includes support for opening, closing, and finding resources, setting attributes, retrieving attributes, and generating events on resources.
The part of VISA that defines the basic constraints and interface definition for the creation and use of a VISA resource. Each VISA resource must derive its interface from the VISA resource template.
A software utility that initializes and prepares a VXI system for use. The VXI Resource Manager is part of the Agilent IO Libraries Suite.
See "notification area".