HP 54501A - Remote, Local; Local Lockout

Each device
on
the
HP-IB
resides
at
a
particular
address,
ranging
from
0
to 30.
The
active
controller
specifies
which
devices
will talk,
and
which will
listen.
•
An
instrument,
therefore,
may
be
talk
addressed,
listen
addressed,
or
unaddressed
by
the
controller.
If
the
controller
addresses the
instrument
to
talk,
it
will
remain
configured
to
talk
until
it
receives
an
interface clear
message
(IFC),
another
instrument's
talk
address
(OTA),
its
own
listen address
(MLA),
or
a
universal
untalk
command (UNT).
If
the
controller addresses
the
instrument
to
listen,
it
will
remain
configured
to
listen until
it
receives
an
interface clear
message
(IFC),
its
own
talk
address
(MTA),
or
a
universal
unlisten
command (UNL).
Remote,
Local
and
Local
Lockout
The
local,
remote,
and
remote
with
local lockout
modes
may
be
used for
various
degrees
of
front-panel
control
while
a
program
is
running.
The
instrument
will
accept
and
execute
bus
commands
while
in
local
mode,
and
the
front
panel
will
also be
entirely
active.
If
the
HP
54501A
is
in
remote
mode,
all
controls
(except
the
power
switch
and
the
LOCAL
key)
are
entirely
locked
out.
Local control
can
only
be
restored
by
the
controller
or
pressing
the
front-panel
LOCAL
key.
Note
Cycling
the
power
will
also
restore local
control,
but
this
will
also
reset
certain
HP-IB states.
The
instrument
is
placed
in
remote
mode
by
setting
the
REN
bus
control
line
true,
and then
addressing
the
instrument
to
listen.
The
instrument
can
be
placed
in
local
lockout mode
by
sending
the
local lockout
command
(LLO).
The
instrument can
be
returned
to
local
mode
by
either
setting
the
REN
line
false,
or
sending
the
instrument
the
go-to-local
command
(GTL),
or
simulating a
front-panel
LOCAL
key
press
using
the
SYSTEM:KEY
command.
Interface Functions
2-2
HP
54501A
Programming