Associated Research HYPOTULTRA III 7620, Руководство по эксплуатации и обслуживанию, Страница: 83 / 148

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8. Bus Remote Interface GPIB / RS-232
This section provides information on the proper use and configuration of bus remote interface.
The RS-232 remote interface is standard on model 76XX but the GPIB (IEEE-488) interface
option can be substituted for the RS-232 interface. Please refer to the Option section of this
manual for details on the HypotULTRA III options. The RS-232 interface also uses the same
command set as the GPIB interface for setting of test parameters. However, many functions of
the GPIB 488.2 interface are not available through RS-232. The IEEE-488 interface included
with HypotULTRA III conforms to the requirements of the IEEE-488.2 standard.
8.1. A Brief History of IEEE-488
Hewlett-Packard designed in 1965 the Hewlett-Packard Interface Bus (HP-IB) to connect their
line of programmable instruments to computers. This bus had high transfer rates (nominally 1
Mbytes/s), and thus quickly gained acceptance. Later, it was accepted as the IEEE Standard
488-1975 and has then evolved into ANSI/IEEE Standard 488.1-1987. An enhancement to this
standard was the IEEE standard 728-1982 and evolved into IEEE Std 488.2-1887. The new
standard 488.2 was created and intended to be used with the existing 488.1 standard. The
488.2 standard defines issues related to standard codes, formats, protocols, and common
commands.
IEEE-488 has expanded over the years and is used with many more types of computers and
instruments than just HP. Because of this, it is usually referred to as the General Purpose
Interface Bus, (GPIB).
8.2. GPIB Messages
There are typically two types of messages that GPIB devices use to communicate with other
interconnected GPIB devices;
Interface messages: Often called commands or command messages and Device dependent
messages often called data or data messages.
Data Messages: Contain information such as programming instructions or measurement
results. Command Messages perform functions such as initializing the bus and addressing and
unaddressing devices.
8.3. Functions
A GPIB device can be a Listener, Talker, and/or Controller. A Talker sends data messages to
one or more Listeners, which receive data. A Controller manages the information flow on the
GPIB by sending commands to all devices. The GPIB bus is much like a computer bus except a
computer has circuit cards connected via a backplane and the GPIB has stand-alone devices
connected via a cable.
8.4. Signals and Lines
The GPIB consists of 16 signal lines and 8 ground-return or shield drain lines. The 16 signal
lines are grouped into 8 data lines, 3 handshake lines, and 5 interface management lines.