National Instruments NI-488.2 Benutzerhandbuch

© National Instruments Corporation

The ANSI/IEEE Standard 488.1-2003, also known as the General Purpose 
Interface Bus (GPIB), describes a standard interface for communication 
between instruments and controllers from various vendors. It contains 
information about electrical, mechanical, and functional specifications. 
GPIB is a digital, 8-bit parallel communications interface that supports 
both interlocked and noninterlocked handshaking. The interlocked 
handshake, also known as three-wire handshake, allows for data transfer 
rates of 1 Mbyte/s and higher. The noninterlocked handshake, also known 
as HS488, allows for data transfer rates up to 8 Mbytes/s. The bus supports 
one System Controller, usually a computer, and up to 14 additional 
instruments. The ANSI/IEEE Standard 488.2-1992 extends IEEE 488.1 by 
defining a bus communication protocol, a common set of data codes and 
formats, and a generic set of common device commands.

GPIB devices can be Talkers, Listeners, or Controllers. A Talker sends out 
data messages. Listeners receive data messages. The Controller, usually 
a computer, manages the flow of information on the bus. It defines the 
communication links and sends GPIB commands to devices.

Some devices are capable of playing more than one role. A digital 
voltmeter, for example, can be a Talker and a Listener. If your system 
has a National Instruments GPIB interface and software installed, it can 
function as a Talker, Listener, and Controller.

You can have multiple Controllers on the GPIB, but only one Controller at 
a time can be the active Controller, or Controller-In-Charge (CIC). The CIC 
can be either active or inactive (standby). Control can pass from the current 
CIC to an idle Controller, but only the System Controller, usually a GPIB 
interface, can make itself the CIC.