Associated Research HypotULTRA II 7500DT, Руководство по эксплуатации и обслуживанию

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OPERATION
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8. Bus Remote Interface GPIB / RS-232
This section provides information on the proper use and configuration of the GPIB
and RS-232 interfaces. The GPIB (IEEE-488) remote interface is standard on
model 7500DT and 7504SA. The RS-232 interface can be substituted for the GPIB
interface. The RS-232 interface also uses the same command list as the GPIB with
the exception of the SRQ functions.
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 since evolved into
ANSI/IEEE Standard 488.1-1987.
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.
Data Lines: The eight data lines, DI01 through DI08 carry data and command
messages. The 7-bit ASCII or ISO code set is used and the eighth bit DI08 is unused.
Handshake Lines: The transfer of message bytes between devices is done via three
asynchronously control lines. Referred to as three-wire interlocked handshake.