Remote Control Of Devices; Locking Out Local Control - HP 9000 Series 300 Tutorials Manual

Remote Control of Devices
Most HP-IB devices can be controlled from either their front panel or the bus.
If the device's front-panel controls are currently operational, the device is in
local state. If it is being controlled through the HP-IB, it is in remote state.
Pressing the device's front-panel LOCAL key returns the device to local control
unless it has been placed in local lockout state (described in the next section).
Whether the HP-IB remote enable (REN) line is asserted or not determines
whether or not a device can respond to remote program control. While REN
is asserted, any device that is addressed to listen is automatically placed in
remote state. Only the System Controller can assert or release the REN line.
REN, by default, is asserted at power-up and remains asserted unless changed
as discussed later in this chapter under the topic System Controller Operations.
Locking Out Local Control
The LOCAL LOCKOUT command inhibits the LOCAL key or switch present
on the front panel of most HP-IB devices, thus preventing anyone from
interfering with system operations by pressing front-panel control buttons. All
devices that support local lockout are locked, whether addressed or not, and
cannot be returned to local control from their front panels.
The following code segment shows one method for sending the LOCAL
LOCKOUT command:
command [0]
=
17; /* Decimal value of LOCAL LOCKOUT*/
hpib_send_cmnd(eid. command. 1);
The GO TO LOCAL command can be used to place a device in local
(front-panel control) state.
Controlling the HP-IB Interface 3-25