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a. Linear Configuration
The standard connector is the Amphenol or Cinch Series 57 Microribbon or Amp Champ type.
For special interconnection applications, you use an adapter cable using a non-standard cable
and/or connector.
The GPIB uses negative logic with standard TTL (transistor-transistor logic) level. For
example, when DAV is true, it is a TTL low level (≤ 0.8 V), and when DAV is false, it is a
TTL high level (≥ 2.0 V).
Configuration Requirements
To achieve the high data transfer rate that the GPIB was designed for, you must limit the
number of devices on the bus and the physical distance between devices. The following
restrictions are typical:
•
A maximum separation of 4 m between any two devices and an average separation of 2 m
over the entire bus.
•
A maximum total cable length of 20 m.
•
A maximum of 15 devices connected to each bus, with at least two-thirds powered on.
For high-speed operation, the following restrictions apply:
•
All devices in the system must be powered on.
•
Cable lengths must be as short as possible with up to a maximum of 15 m of cable for
each system.
•
There must be at least one equivalent device load per meter of cable.
If you want to exceed these limitations, you can use a bus expander to increase the number of
device loads. You can order bus expanders from NI.
20 | ni.com | GPIB-140B User Manual
Figure 14. Linear and Star System Configuration
Device A
Device B
Device C
Device A
Device B
b. Star Configuration
Device D
Device C
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