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HP IBASIC Supplement 8-11

Interfacing with External Devices

General Bus Management

Host Instrument

The Local Lockout message is not supported for the host instrument

since front panel control is always necessary in order to pause or abort

the program. Specifying the internal interface in a LOCAL LOCKOUT

statement will not generate an error, but will have no effect.

LOCAL

During system operation, it may be necessary for an operator to interact

with one or more external devices. For instance, an operator might need

to work from the front panel to make special tests or to troubleshoot. It is

also good systems practice to return all devices to local control when

remote-control operations are complete. Executing the LOCAL statement

returns the speciﬁed devices to local (front panel) control.

If primary addressing is speciﬁed, the Go-to-Local message is sent only

to the speciﬁed device(s). However, if only the interface select code is

speciﬁed (LOCAL 7), the Local message is sent to all devices on the

external interface and any previous Local Lockout message (which is still

in effect) is automatically cleared.

Host Instrument

The LOCAL 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 LOCAL statement will not generate

an error.

TRIGGER

The TRIGGER statement sends a Trigger message to a selected device or

group of devices. The purpose of the Trigger message is to initiate some

device-dependent action; for example, it can be used to trigger a digital

voltmeter to perform its measurement cycle. Because the response of a

device to a Trigger message is strictly device-dependent, neither the

Trigger message nor the interface indicates what action is initiated by

the device.

Specifying only the interface select code outputs a Trigger message to all

devices currently addressed to listen on the bus. Including a device

address in the statement triggers only the device addressed by the

statement.

Agilent Technologies 8712ET User's Handbook Supplement

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