Agilent Technologies X Series Manual page 456

Input/Output
Initial S/W Revision A.04.00
External Ref Coupling
Only appears with option ERC installed and licensed.
This function lets you couple the sweep system of the analyzer to the state of the External Reference. If
Normal is selected, data acquisition proceeds regardless of the state of the External Reference. When
you select Ext Ref Out Of Range Stops Acquisition , the data acquisition (sweep or measurement) stops
when either the "521, External ref out of range" or the "503, Frequency Reference unlocked" error
message is asserted. Note that this will only take place if the Freq Ref In selection is External .
With the acquisition stopped, the data display will stop updating (even if this occurs in the middle of a
sweep or measurement) and no data will be returned to a READ? or MEASure? query; that is, these
queries will not complete because the analyzer will not respond to them. Furthermore, no response will
be generated to a *WAI? or *OPC? query.
Proper SCPI sequences are shown below, which will always fail to return if the acquisition stops during
the requested sweep or measurement. Note that, for predictable operation of this function, it is best to
operate the analyzer in single measurement mode (INIT:CONT OFF), because if operating in continuous
mode, the analyzer may respond to the above queries even after the acquisition stops, with data left over
from the previous acquisition.
:INIT:CONT OFF
:INIT:IMM;*OPC?
--
:INIT:CONT OFF
:INIT:IMM;*WAI?
--
:INIT:CONT OFF
:READ?
--
:INIT:CONT OFF
:MEASure?
When the acquisition ceases, in addition to the error condition(s) described above, a popup error message
will be generated informing you that the acquisition has ceased due to an invalid external reference. This
message will stay on the screen while the acquisition is suspended.
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