Remote, Local; Local Lockout - HP 54501A Programming Reference Manual

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