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Model 8902A
Opera tion
Clear Lockout/Set Local
The Measuring Receiver returns to local operation when it receives the Clear Lockout/Set Local
message.
NOTE
CIsav
Lockoirt/Sct
Local can bc accomplished
by
switching lhc power
10
STBY
and hack
to
ON. Rvlitrning
lo
Local optv-alion in lhis way has lhr following
disadvan t agtx
0
II
defiats [he pitrpose
of
Local Lockoitt (rhal is, the
syslcm
controller will
lose conlrol o f /he Measiiring Receiver).
e
instrirment configitration is rtwt
to
Powcr-iip conditions listed in the
Detailed Operating Instructions itndcr tYn.striimcnf Prtwt"
on page
3-23 9.
Service Request Message
(SRQ)
The Service Request Message (SRQ message) is being issued when the SRQ
bus
line
is
asserted and
the SRQ light on the front panel is lit by the instrument. The Service Request message may be issued
under following conditions:
0
the instrument requires re-calibration or is uncalibrated,
0
there has been a Frequency Offset mode change,
0
an enabled limit has been exceeded,
0
an instrument error has occurred,
0
an HP-IB code error has occurred,
e
measurement data is ready to be read.
The Measuring Receiver uses it.s Status Byte and the SRQ Mask (Special Function 22) t o determine
whether or not to issue a SRQ message. Refer to Figure 3-4, "Issuing a Service Request Message"
throughout the following discussion of the Service Request Message, SRQ Mask and the Status Byte.
The Service Request Message is asserted when the RQS bit of the Status Byte is set by the instrument.
The RQS bit is set automatically when one or more of the other bits in the Status Byte are set.
For
the bits other than the RQS bit of the Status Byte to be set, those bits must be enabled by the SRQ
Mask before the instrument condition which will set them occurs.
The instrument can send the Service Request message in either local or remote operation.
Clearing the Service Request Message After the Service Request message has been sent, it will be
cleared when the Status Byte is cleared which is described below under 5tatus Byte".
3-27
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