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SECTION 4
GPIB Interface
4.1
INTRODUCTION
The GPIB Interface
is a general-purpose
interface
bus
system recognized by the IEEE (Institute of Electrical and
Electronics Engineers)
in 1975 in the US and is a method
of standardizing
the data input/output
transfer between
measuring
instruments
and peripherals
including
re-
mote control functions.
By designing
each controller and peripheral
device into
an interface conforming
to this standard, it is possible to
establish complete hardware compatibility
between each
device.
Up to 15 devices may be connected to a single interface
bus with data transfer performed
by three handshake
lines. These handshake lines ensure reliable data transfer
between
data senders and receivers
even though they
may have different transfer rates.
Various names have been applied to the GPIB, including
IEEE488
bus. The official name, however, is the "IEEE-
Std 488-1978:
IEEE Standard
Digital Interface
for Pro-
grammable
Instrumentation."
It has virtually the same specifications
as the IEC bus, al-
though the connector differs, making it usable with this
bus by means of connector adapters.
4.1 .I
Major GPIB Specifications
l
Overall cable length: 20m max.
l
Cable lengths between device: 4m max.
l
Number of devices on bus (including
controller):
15
max.
l
Transfer method: 3 Handshake
Lines
l
Transfer rate: 1M bytes/s (max.)
l
Data transfer: 8 Bits parallel
0 Signal lines:
Data bus: 8 Lines
Control bus: 8 Lines
Handshake
lines: DAV, NRFD and NDAC
Control lines: ATN, REN, IFC, SRQ and EOI
Signal/system
grounds: 8 Lines
l
Signal logic: Negative
True (low-level):
0.8V max.
False (high-level):
2.OV min.
l
Interface Connector: See Figure 4-1
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4-l
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