HP 3468A - Appendix A: HP-IL Description; Introduction to HP-IL; General HP-IL System Description

Introduction
Hewlett-Packard
Interface
Loop
(HP-IL)
is
a
two
wire
interface
that
permits
com-
munication
from
one
device
or
instrument
to
another.
As
the
name
implies,
devices
are
connected
in
a
serial
loop
structure.
Data
or
information,
in
the
form
of
digital
messages,
travels
from
one
device
to
the
next
around
the
loop.
The
following
discussion
is
controller
independent
but,
where
appropriate,
is
dependent
on the 3468A.
General
HP-IL
Description
The
interface
loop
consists
of
a
calculator/controller
and
up
to
30
peripheral
devices
such
as
the
3468A,
printer/plotters,
etc.
Maximum
cable
length
from
one
device
to
the
next
should
not
exceed
10
meters
to
maintain
noise
immunity.
Infor-
mation
is
transferred
from
one
device
to
the
next
around
the
loop.
If
the
informa-
tion
is
not
intended
for
a
particular
device
(see
paragraph
on
addressing),
the
device
merely
passes
the
information
on
to
the
next
device
in
the
loop.
When
the
information
reaches
the
intended
device,
the
device
responds
as
directed
by
the
information.
In
this
way,
the
calculator/controller
can
send
information
to
and
receive
information
from
selected
devices
in
the
loop
according
to
the
devices
capabilities.
Figure
A-1
shows
a
typical
interface
loop
system.
ADDRESS 1 ADDRESS 2
VOLTMETER
LISTENER
ADDRESS:
0)
ADDRESS
3
TALKER
LISTENER
CALCULATOR
TALKER
CONTROLLER
3468 AP=1
ss 4
Figure
A-1.
Typical
HP-IL
System
37