Bus Remote Interface Gpib / Rs-232; A Brief History Of Ieee-488; Gpib Messages - Associated Research 7704 Operation And Service Manual

8. Bus Remote Interface GPIB / USB/RS-232
This section provides information on the proper use and configuration of the GPIB and
USB/RS-232 interfaces. The USB/RS-232 remote interface is standard on model 7700
and 7704. The GPIB (IEEE-488) interface can be substituted for the USB/RS-232
interface.
The USB/RS-232 interface card requires the user to download a driver in order for the
instrument to recognize the USB interface. The driver can be found on the Associated
Research, Inc. website:
http://www.asresearch.com/products/software/USB-driver.aspx
Click on "USB/RS-232 Driver" to download the driver. This link contains an automatic
extract and install program. Follow the instructions of the installation program to
initialize the driver install. NOTE: The USB port acts as a USB to RS-232 converter. As
a result, the PC will recognize the USB port as a virtual COM port.
The USB/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.
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