8-10 HP IBASIC Supplement
Interfacing with External Devices
General Bus Management
REMOTE
Most GPIB devices can be controlled from the front panel or from the
bus. If the device's front panel controls are currently functional, it is in
the Local state. If it is being controlled through the GPIB, it is in the
Remote state. Unless operating in the Local Lockout mode, each GPIB
device has method (usually a key) to return itself to Local (front panel)
control.
When the analyzer is being controlled by a program running on an
external controller, the softkey is always available to
return the analyzer to Local control.
The Remote message is automatically sent to all devices whenever the
system controller is powered on, reset, or when it sends the Abort
message. A device also enters the Remote state automatically whenever
it is addressed. The REMOTE statement also outputs the Remote message,
which causes all (or specified) devices on the bus to change from local
control to remote control. The host instrument must be designated as the
system controller before an IBASIC program can execute the REMOTE
statement on select code 7.
Host Instrument
The REMOTE statement has no effect on the host instrument since it is
always in remote control whenever an IBASIC program is running.
Specifying the internal interface in a REMOTE statement will not
generate an error, but will have no effect.
LOCAL LOCKOUT
The Local Lockout message effectively locks out the “local” switch
present on most GPIB device front panels. It maintains system integrity
by preventing a user from interfering with system operations by pressing
buttons. As long as Local Lockout is in effect, no bus device can be
returned to local control from its front panel.
The Local Lockout message is sent by executing the LOCAL LOCKOUT
statement. This message can be sent to all devices on the external
interface by specifying the bus address (7). Specifying a single address on
the bus (i.e. 722) sends the command to only the device at that address.
The Local Lockout message is cleared when the Local message is sent by
executing the LOCAL statement. However, executing the ABORT
statement does not cancel the Local Lockout message.
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