Newport FPM-8220, User Manual

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April 2018 24 FPM-8220
Basic GPIB Concepts
The basic GPIB concepts are not necessary to successfully operate the FPM-8220, but are a
useful perspective in understanding GPIB communication.
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 (see below). The end of this chapter includes information
on interface messages supported by the FPM-8220.
Talkers, Listeners, and Controllers
Every GPIB system consists of one or more talkers, listeners and often at least one controller.
Talkers supply data and listeners accept data. 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.
If there is more than one controller, only one can be the Controller In Charge (CIC). Control can be
passed from one computer to another. In a multiple controller system, there can be one System
Controller capable of asserting control and becoming the CIC.
GPIB Cable Connections
Standard GPIB connectors can be connected together (stacked) allowing the system to be
configured linearly, or in a star configuration, which is shown in Figure 3.1.