LDC-3700 Series
37
C H A P T E R
3
R
EMOTE
O
PERATION
GPIB (General Purpose Interface Bus) is the common name for
ANSI/IEEE Standard 488.2 1987
,
an industry standard for interconnecting test instruments in a system. Everything you can do from
the front panel can also be done remotely, and in some cases, with more flexibility. For instance, in
remote mode, you have access to commands for functions not found on the front panel, such as
commands that will increment (INC) and decrement (DEC) the current set point by a pre−defined
step value. Also, you may only query the TEC voltage via remote control. The following sections
show you the fundamentals of operating your LDC−3700B Laser Diode Controller remotely through
the GPIB interface.
Basic GPIB Concepts
The information in this basic concepts discussion is normally not necessary to successfully operate
the LDC−3700B through its GPIB interface, because your computer’s GPIB controller usually
handles them for you. However this is a useful perspective in understanding GPIB.
Data and Interface Messages
GPIB devices communicate with each other by sending data and interface messages. Data contains
device−specific information such as programming instructions, measurement results, and instrument
status. Each device has an address number, and ignores all data traffic not addressed to it.
Depending on its content, data is often called a "device dependent message" or a "device
dependent command". Interface messages manage the bus, with functions such as initializing the
bus and addressing or unaddressing devices. In addition, some individual bus lines are designated
for this purpose.
Talkers, Listeners, and Controllers
Every GPIB system consists of one or more "talkers" and "listeners", and often at least one
"controller". Talkers supply data. Listeners accept data. A system can consist of simply a talker
and listener, for example a meter connected to a datalogger or chart recorder. Controllers designate
talkers and listeners. A controller is necessary when the active talkers or listeners must be changed.
When the controller is a computer, it often also designates itself as a listener so it can collect data
from designated talkers.
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