Omega Products CPCI-GPIB Installation Manual
User's Guide
http://www.omega.com
e-mail: info@omega.com
GPIB HARDWARE MANUAL
FOR USE WITH
PCI-GPIB, ISA-GPIB
CHAPTER ONE: INTRODUCTION ......................
CHAPTER TWO: INSTALLATION ...................
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11.1 HISTORY ..........................................
11.2 GPIB SYSTEM DESCRIPTION ........................
11.2.1 Talkers, Listeners, and Controllers ..................
21.2.2 GPIB Electrical Signal Configuration ................
31.2.3 Connection Configurations .........................
5
52.1 PCI-GPIB ..........................................
62.2 ISA-GPIB ..........................................
82.3 ISA-GPIB/LC .......................................
102.4 PCM-GPIB ........................................
112.4.1 Windows 95 ....................................
112.4.2 Windows 3.1 ...................................
122.5 PC104-GPIB .......................................
142.6 CPCI-GPIB ........................................
Chapter One: INTRODUCTION
1.1 HISTORY
The GPIB (General Purpose Interface Bus) has become the worldwide standard for
connecting instruments to computers. Invented in the 1960s by Hewlett Packard and
originally designated as HPIB, the bus specification was eventually adopted by a wide
variety of both instrument and computer manufacturers. The original specification was
documented and sanctioned by the Institute of Electrical and Electronic Engineers as
IEEE-488.
The advent of the inexpensive and powerful personal computer has driven the GPIB
market through explosive gr owth. As GPIB bus usage expanded, ther e arose the ne ed
for some additional capability and standardization, so in 1987, IEEE-488.2 was
adopted. IEEE-488.2 was revised/ammended in 1992 and represents the current GPIB
specification. The new specification provides some standardization among compliant
instruments. These standardization greatly simplifies the job of the GPIB system
designer since 488.2 compliant instruments share common programming conventions.
1.2 GPIB SYSTEM DESCRIPTION
1.2.1 Talker
A GPIB device can be a
Talker sends data to one or more Listeners, A Listener accepts data from a Talker and
a Controller manages the flow of information over the bus. A GPIB Digital Voltmeter
is acting as a Listener as its input configurations and ranges are set, and then as a
Talker when it actually sends its readings to the computer.
The Controller is in charge of all communications over the bus. The Controller’s job
is to make sure only one device tries to talk at a time, and make sure the correct Listeners are paying attention when the Talker talks. Each GPIB system has a single system controller. The system controller is ultimately in charge of the bus, and is in
control as the bus is powered up. There can be more than one Controller on the bus
and the System Controller can pass active control to another controller capable device,
though only one can be Controlle r In Charge at a given time. The
GPIB board is usually designated as the System Controller.
1.2.2 GPIB Electrical Signal Configuration
Listeners
s,
Controllers
, and
Talker, Listener
, and/or
1
Controller
. As the name implies a
The GPIB is an 8-bit parallel data tr ansfer bus. In addition to the 8 data bits, the bus
carries three handshaking lines and five GPIB specific management and control lines.
The remainder of the standard 24 pin GPIB cable is used for the cable shield, signal
grounds and returns. The GPIB connector pin-out is shown in the diagram below:
Standard GPIB Cable/Connector
DATA LINES
DIO1 through DIO8 are the data transfer bits. Most GP IB systems send 7-bit data
and use the eight bit as a parity or disregard it entirely
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HANDSHAKING LINES
There are three handshaking lines that control the data transfer between devices.
NRFD (Not Ready For Data): this bit is used to indicate the readiness (or lack
thereof) of a device to accept data
DAV (Data Valid): bit is used to indicate to receiving devices that data has been
placed on the bus and is available to read.
NDAC (Not Data Accepted): is asserted by the receiving device to indicate that data
has been read and may now be removed from the bus.
SYSTEM MANAGEMENT LINES
ATN (Attention): is used by the controller to specify how data on the DIO lines is
interpreted and which devices must respond to the data
IFC (Interface Clear): is used by the system controller to place the entire system in a
known quiescent (Cleared) state and to assert itself as Controller In Charge (CIC).
SRQ (Service Request): is used by a device on the bus to indicate the need for attention and requests an interrupt of the current event sequence.
REN (Remote Enable): is used by the controller in conjunction with other messages
to place a device on the bus into either remote or local mode
EOI (End or Identify): Is used by Talkers to indicate the end of a message string, or
is used by the Controller to command a polling sequence.
1.2.3 Connection Configurations
The GPIB specification is quite definitive regarding the number of devices and cable
lengths allowed in a GPIB system. There can be no more than 15 devices on a single
contiguous GPIB bus. Larger systems are possible by installing additional GPIB interface boards in your computer
The maximum, total length of all cables on a single GPIB system is 20 meters. In
addition, cable length between consecutive devices may be no greater than 4 meters,
and average cable length must be 2 meters or less. Stated another way, the total cable
length (in meters) in the system may not be longer than 2 times the number of devices
(up to 20 meters). Longer length systems are possible, but only with the use of a GPIB
extender card.
In addition to the above rules, at least two thirds of all devices on the bus should be
powered on for proper operation.
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Keeping the above constraints in mind, there is no limitation on the actual connection
scheme used to connect the GPIB devices together. Star, Linear or any combination of
both may be used. These are shown in the following diagrams.
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Linear Connection
Configuration
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Star Connection
Configuration
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