UPGRADED
STANDARD BOOSTS SPEED OF IEEE 488 INSTRUMENT BUSES EIGHTFOLD
Contact:
Karen McCabe, IEEE Senior Marketing Manager
+1 732 562 3824, k.mccabe@ieee.org
PISCATAWAY,
N.J., USA, 6 Oct. 2003 The need for higher-performing buses
in laboratory and manufacturing instruments has prompted the Institute
of Electrical and Electronics Engineers to upgrade its IEEE 488.1(TM)
standard so IEEE 488 buses can transfer data at speeds as high
as 8 MB/s (megabytes per second), up from 1 MB/s. The increased
throughput rests on the use of two-wire handshaking and packed
data streaming. The prior version only allowed three-wire handshaking
and handshaking after each byte.
The revised
standard, IEEE 488.1-2003, "Standard for Higher Performance
Protocol for the Standard Digital Interface for Programmable Instrumentation,"
addresses the operation of the IEEE 488 bus or General Purpose
Interface Bus (GPIB), which has been in use for over 25 years
and is built into millions of instruments worldwide. These buses
allow communication among controllers (usually a computer) and
instruments in research, test and production settings, such as
oscilloscopes, spectrum analyzers and digital multimeters.
The new specification
defines a "non-interlocked" handshaking protocol between
devices using only two control lines, which transfers data faster
while still ensuring data integrity. The existing "interlocked"
handshaking protocol depends on three control lines for handshaking.
Devices that comply with the new version of IEEE 488.1 will be
backward compatible with those operating under the existing protocol
and can be used with those older instruments on the same physical
bus.
Newer devices
will default to the three-wire, 1-MB/s mode when working with
older systems. In addition, existing IEEE 488 instruments are
fully compatible with the revised standard but cannot take advantage
of the higher data transfer rates.
"This
revision, the first since 1987, reflects the high interest in
a better-performing IEEE 488 bus," says Robert Canik, IEEE
488 Working Group Chair. "It extends the usefulness of this
tried and true bus standard and makes it even more viable for
years to come.
"Although
alternate connectivity options exist, such as those based on Ethernet
and USB protocols, the IEEE 488 bus offers a range of benefits
that favor its use in many situations. For instance, it is designed
specifically for test and measurement applications. The bus also
uses rugged, industrial cabling and connectors and avoids the
security and other issues that can accompany options associated
with broad networks."
In complying
with the new standard, instrument makers need not make hardware
or panel labeling changes because the high-speed capability is
optional. Instrument manufacturers who would like to support the
new high-speed IEEE 488 transfer protocol can do so by adding
a readily available controller IC to their design.
Canik notes
that several instrument vendors participated in creating the new
specification because the IEEE 488 bus is integral to such a large
installed-instrument base. "After decades of use, this bus
is nearly universal in the test and measurement industry,"
he says. "The updated standard reinforces the use of the
GPIB in current and future systems."
About the
IEEE Standards Association
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IEEE 488 and
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are the trademarks, service marks or registered trademarks of
their respective holders.
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