Glossary

NI-488.2

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Glossary

Prefixes

Symbol	Prefix	Value
p	pico	10 ^-12
n	nano	10 ^-9
µ	micro	10 ^-6
m	milli	10 ^-3
k	kilo	10 ³
M	mega	10 ⁶
G	giga	10 ⁹
T	tera	10 ¹²

A
acceptor handshake	Listeners use this GPIB interface function to receive data, and all devices use it to receive commands. See source handshake and handshake.
access board	The GPIB interface that controls and communicates with the devices on the bus that are attached to it.
ANSI	American National Standards Institute.
API	Application Programming Interface.
application interface	Formerly called language interface. Code that enables an application program that uses NI-488.2 calls to access the driver.
ASCII	American Standard Code for Information Interchange.
asynchronous	An action or event that occurs at an unpredictable time with respect to the execution of a program.
automatic serial polling	A feature of the NI-488.2 software in which serial polls are executed automatically by the driver whenever a device asserts the GPIB SRQ line.
B
base I/O address	See I/O address.
BIOS	Basic Input/Output System.
board-level function	A rudimentary function that performs a single operation.
C
CFE	Configuration Enable. The GPIB command which precedes CFGn and is used to place devices into their configuration mode.
CFGn	These GPIB commands (CFG1 through CFG15) follow CFE and are used to configure all devices for the number of meters of cable in the system so that HS488 transfers occur without errors.
CIC	Controller-In-Charge. The device that manages the GPIB by sending interface messages to other devices.
CPU	Central processing unit.
D
DAV	Data Valid. One of the three GPIB handshake lines. See handshake.
DCL	Device Clear. The GPIB command used to reset the device or internal functions of all devices. See SDC.
device-level function	A function that combines several rudimentary board operations into one function so that the user does not have to be concerned with bus management or other GPIB protocol matters.
DIO1 through DIO8	The GPIB lines that are used to transmit command or data bytes from one device to another.
DLL	Dynamic link library.
DMA	Direct memory access. High-speed data transfer between the GPIB interface and memory that is not handled directly by the CPU. Not available on some systems. See programmed I/O.
driver	Device driver software installed within the operating system.
E
END or END Message	A message that signals the end of a data string. END is sent by asserting the GPIB End or Identify (EOI) line with the last data byte.
EOI	A GPIB line that is used to signal either the last byte of a data message (END) or the parallel poll Identify (IDY) message.
EOS or EOS Byte	A 7- or 8-bit end-of-string character that is sent as the last byte of a data message.
EOT	End of transmission.
ESB	The Event Status bit is part of the IEEE 488.2-defined status byte which is received from a device responding to a serial poll.
G
GET	Group Execute Trigger. It is the GPIB command used to trigger a device or internal function of an addressed Listener.
GPIB	General Purpose Interface Bus is the common name for the communications interface system defined in ANSI/IEEE Standard 488.1-1987, ANSI/IEEE Standard 488.1-2003, ANSI/IEEE Standard 488.2-1987, and ANSI/IEEE Standard 488.2-1992.
GPIB address	The address of a device on the GPIB, composed of a primary address (MLA and MTA) and perhaps a secondary address (MSA). The GPIB interface has both a GPIB address and an I/O address.
GPIB interface	Refers to the National Instruments family of GPIB interfaces.
GTL	Go To Local. It is the GPIB command used to place an addressed Listener in local (front panel) control mode.
H
handshake	The mechanism used to transfer bytes from the Source Handshake function of one device to the Acceptor Handshake function of another device. The three GPIB lines DAV, NRFD, and NDAC are used in an interlocked fashion to signal the phases of the transfer, so that bytes can be sent asynchronously (for example, without a clock) at the speed of the slowest device. For more information about handshaking, refer to the ANSI/IEEE Standard 488.1-1987 and ANSI/IEEE Standard 488.1-2003.
hex	Hexadecimal; a number represented in base 16. For example, decimal 16 = hex 10.
high-level function	See device-level function.
HS488	High-speed data transfer protocol, part of the IEEE 488.1-2003 specification.
Hz	Hertz.
I
ibcnt	After each NI-488.2 I/O call, this global variable contains the actual number of bytes transmitted. On systems with a 16-bit integer, such as MS-DOS, ibcnt is a 16-bit integer, and ibcntl is a 32-bit integer. For cross-platform compatibility, use ibcntl, unless using the newer NI4882 API. For accessing the newer NI4882 API, use the global function, Ibcnt, instead.
Ibcnt	After each NI-488.2 call, this global function contains the actual number of bytes transmitted. The Ibcnt function returns a 32-bit integer. For accessing the newer NI4882 API, this function is recommended instead of the global variables, ibcnt and ibcntl.
ibcntl	After each NI-488.2 I/O call, this global variable contains the actual number of bytes transmitted. On systems with a 16-bit integer, such as MS-DOS, ibcnt is a 16-bit integer, and ibcntl is a 32-bit integer. For cross-platform compatibility, use ibcntl, unless using the newer NI4882 API. For accessing the newer NI4882 API, use the global function, Ibcnt, instead.
iberr	A global variable that contains the specific error code associated with a function call that failed. For accessing the newer NI4882 API, use the global function, Iberr, instead.
Iberr	A global function that contains the specific error code associated with a function call that failed. For accessing the newer NI4882 API, this function is recommended instead of the global variable, iberr.
ibsta	At the end of each function call, this global variable (status word) contains status information. For accessing the newer NI4882 API, use the global function, Ibsta, instead.
Ibsta	At the end of each function call, this global function contains status information. For accessing the newer NI4882 API, this function is recommended instead of the global variable, ibsta.
IEEE	Institute of Electrical and Electronic Engineers.
interface message	A broadcast message sent from the Controller to all devices and used to manage the GPIB.
I/O	Input/output. In the context of this documentation, the transmission of commands or messages between the computer through the GPIB interface and other devices on the GPIB.
I/O address	The address of the GPIB interface from the point of view of the CPU, as opposed to the GPIB address of the GPIB interface. Also called port address or board address.
ist	An Individual Status bit of the status byte used in the Parallel Poll Configure function.
L
LAD	Listen address. See MLA.
Listener	A GPIB device that receives data messages from a Talker.
LLO	Local Lockout. The GPIB command used to tell all devices that they may or should ignore remote (GPIB) data messages or local (front panel) controls, depending on whether the device is in local or remote program mode.
low-level function	A rudimentary board or device function that performs a single operation.
M
m	Meters.
MAV	The Message Available bit is part of the IEEE 488.2-defined status byte which is received from a device responding to a serial poll.
MLA	My Listen Address. A GPIB command used to address a device to be a Listener. It can be any one of the 31 primary addresses.
MSA	My Secondary Address. The GPIB command used to address a device to be a Listener or a Talker when extended (two byte) addressing is used. The complete address is a MLA or MTA address followed by an MSA address. There are 31 secondary addresses for a total of 961 distinct listen or talk addresses for devices.
MTA	My Talk Address. A GPIB command used to address a device to be a Talker. It can be any one of the 31 primary addresses.
multitasking	The concurrent processing of more than one program or task.
N
NDAC	Not Data Accepted. One of the three GPIB handshake lines. See handshake.
NRFD	Not Ready For Data. One of the three GPIB handshake lines. See handshake.
P
parallel poll	The process of polling all configured devices at once and reading a composite poll response. See serial poll.
PIO	See programmed I/O.
PPC	Parallel Poll Configure. It is the GPIB command used to configure an addressed Listener to participate in polls.
PPD	Parallel Poll Disable. It is the GPIB command used to disable a configured device from participating in polls. There are 16 PPD commands.
PPE	Parallel Poll Enable. It is the GPIB command used to enable a configured device to participate in polls and to assign a DIO response line. There are 16 PPE commands.
PPU	Parallel Poll Unconfigure. It is the GPIB command used to disable any device from participating in polls.
programmed I/O	Low-speed data transfer between the GPIB interface and memory in which the CPU moves each data byte according to program instructions. See DMA.
R
resynchronize	The NI-488.2 software and the user application must resynchronize after asynchronous I/O operations have completed.
RQS	Request Service.
S
s	Seconds.
SDC	Selected Device Clear. The GPIB command used to reset internal or device functions of an addressed Listener. See DCL.
semaphore	An object that maintains a count between zero and some maximum value, limiting the number of threads that are simultaneously accessing a shared resource.
serial poll	The process of polling and reading the status byte of one device at a time. See parallel poll.
service request	See SRQ.
source handshake	The GPIB interface function that transmits data and commands. Talkers use this function to send data, and the Controller uses it to send commands. See acceptor handshake and handshake.
SPD	Serial Poll Disable. The GPIB command used to cancel an SPE command.
SPE	Serial Poll Enable. The GPIB command used to enable a specific device to be polled. That device must also be addressed to talk. See SPD.
SRQ	Service Request. The GPIB line that a device asserts to notify the CIC that the device needs servicing.
status byte	The IEEE 488.2-defined data byte sent by a device when it is serially polled.
status word	See Ibsta.
synchronous	Refers to the relationship between the NI-488.2 calls and a process when executing driver calls is predictable; the process is blocked until the driver completes the function.
System Controller	The single designated Controller that can assert control (become CIC of the GPIB) by sending the Interface Clear (IFC) message. Other devices can become CIC only by having control passed to them.
T
TAD	Talk Address. See MTA.
Talker	A GPIB device that sends data messages to Listeners.
TCT	Take Control. The GPIB command used to pass control of the bus from the current Controller to an addressed Talker.
timeout	A feature of the NI-488.2 driver that prevents I/O calls from hanging indefinitely when there is a problem on the GPIB.
TLC	An integrated circuit that implements most of the GPIB Talker, Listener, and Controller functions in hardware.
U
ud	Unit descriptor. A variable name and first argument of each function call that contains the unit descriptor of the GPIB interface or other GPIB device that is the object of the function.
UNL	Unlisten. The GPIB command used to unaddress any active Listeners.
UNT	Untalk. The GPIB command used to unaddress an active Talker.

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