HP-IB
Bus
Structure
Figure
11-2.
HP-IB
Bus
Structure
Data
Bus
The
data
bus
consists
of
8
bi-directional
lines
that
are
used
to
transfer data
from one
device
to
another
.
Programming
commands
and data
transmitted on
these
lines
are
typically
encoded
in
ASCII,
although
binary
encoding is
often used
to
speed
up
the
transfer
of
large
arrays
.
Both
ASCII-
and binary-data
formats are
available to
the analyzer
.
In
addition,
every
byte
transferred
over
HP-IB
undergoes
a handshake
to insure
valid data.
Handshake Lines
A three-line
handshake scheme
coordinates the
transfer
of
data
between
talkers
and
listeners
.
T
o
insure
data
integrity
in
multiple-listener transfers
,
this
technique
forces
data
transfers
to occur at the transfer rate of
the slowest device connected to the interface
. With most
computing controllers and instruments
, the handshake is
performed automatically
, making it
transparent to the programmer
.
Control Lines
The data bus also has ve control lines
. The controller uses these lines to address devices and
to send bus commands
.
IFC (Interface Clear) This line is used exclusively by the system controller.When
this line is true (low), all devices (whether addressed or not)
unaddress and revert to an idle state.
11-16 Compatible Peripherals
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