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Chapter 1
Introduction
Figure 1-2.
Typical GPIB-120B Expansion System (Logical Configuration)
With the GPIB-120B, you can overcome the following two configuration restrictions imposed
by the ANSI/IEEE Standard 488.1-1987:
•
An electrical loading limit of 15 devices per contiguous bus.
•
A cable length limit of 20 m total per contiguous bus or 2 m multiplied by the number of
devices on the bus, whichever is smaller.
With each GPIB-120B, you can add up to 14 additional devices to the bus. The GPIB-120B
appears as a device load on each side of the expansion; therefore, one GPIB-120B increases the
maximum load limit from 15 devices to 28 devices. The cable length limit for the system is also
increased an additional 4 m to 20 m, depending on the number of devices on that side of the
expansion.
All signal expansion is bidirectional, meaning that Controllers, Talkers, and Listeners can be on
either side of the expander. The GPIB-120B light-emitting diodes (LEDs) indicate the location
of the System Controller, Active Controller, and Source Handshaker, with respect to the two
sides of the expansion.
Because the GPIB-120B is a functionally transparent expander, the same GPIB communications
and control programs that work with an unexpanded system can work unmodified with an
expanded system.
Computer
(Controller, Talker,
and Listener)
Printer
(Listener)
GPIB
Multimeter
(Talker and Listener)
Signal Generator
(Listener)
Unit Under Test