4. The instrument sends the information string
over the bus one byte at a time.
5. The controller recognizes that the string is
terminated.
6. The controller sets the ATN line true.
7. The UNT (untalk) command is placed on the
bus by the controller.
4-12-1. Interrogate Parameter Data Query
The interrogate parameter data query allows access
to information concerning present operating conditions
of the instrument. When the interrogate parameter
data query is given, the Model 8020 will transmit
appropriate data string information the next time the
instrument is addressed to talk. Model 8020 Inter-
rogate Parameter Data Query include:
FRQ? = Interrogate output frequency parameter
AMP? = Interrogate output amplitude parameter
OFS? = Interrogate output offset parameter
WID? = Interrogate pulse width parameter
(model 8021 only)
CAR? = Interrogate Carrier level parameter
(model 8022 only)
STP? = Interrogate logarithmic sweep parameter
(model 8020 only)
SWT? = Interrogate sweep time parameter (model
8020 only)
MRK? = Interrogate logarithmic sweep marker pa-
rameter (model 8020 only)
RPT? = Interrogate internal trigger generator
period parameter
DCO? = Interrogate dc output level parame-
ter(model 8020 and 8022 only)
RPT? = Interrogate trigger period parameter
STT? = Interrogate machine status
For example, model 8020 is asked to return
frequency, amplitude, and offset parameters in a
single <Response Message>
Command: FRQ?;AMP?
Response:FRQ 1.000E+3;AMP 1.00E+0
Table 4-7 shows the general <Response Mes-
sage> format for each of the above commands.
Default values are shown. These defaults are gen-
erated after an SDC or DCL commands.
4-12-2. Common Queries
As discussed in previous paragraphs most instruments
and devices in an ATE system use similar commands
which perform identical functions to avoids the prob-
lem in which devices from various manufacturers
used a different set of commands to enable functions
and report status. Some common commands and
queries, however, are optional; most of them are
mandatory. The following set of common queries are
utilized in the model 8020 (optional common queries
that are not included in the model 8020 command
set will not be discussed here).
*IDN? (Identification Query) - Causes the generator
to respond with its identity. The returned data is
organized into four fields, separated by commas.
The unit must respond with its manufacturer and
model number in the first two fields and may also
report its serial number and options in field three
and four. If the later information is not available, the
device must return an ASCII 0 for each. For example,
model 8021 response to *IDN? is TA-
BOR,8021,0,REV2.0.
*OPC? (Operation Complete Query) - causes the
device to generate the operation complete message
in the Standard Event Status Register when all
pending selected device operations have been fin-
ished.
*SRE? (Service Request Enable Query) - enables
the user to read the contents of the Service Request
Enable register. The device returns a number in the
range of 0 to 63 or 128 to 191, since bit 6 (RSQ)
cannot be set. The binary equivalent of the number
represents the value of the bits of the Service
Request Enable Register.
*STB? (Read Status Byte Query) - Reads the
status byte containing the master summary status
(MSS) bit. The device responds with an integer in
the range of 0 to 255, whose binary equivalent
represents the value of the bits of the status byte.
*TST? (Self-Test Query) - Tells the device to
perform an internal self-test and report back to the
controller if any errors are detected. The generator
responds to this query with a number. A value of
1 in the response indicates that the self-test routine
has detected an error. A value of 0 in the response
indicates that the self-test was carried out success-
fully.
4-12-3. Response Header (X)
The <Response Header> from the <Response Mes-
sage> string may be suppressed using this command.
When the <Response Header> is suppressed the
output data string is 3 byte shorter. The <Response
Header> may be suppressed using the following
commands:
X0 = Response header OFF
X1 = Response header ON
Model 8020 IEEE-488.2 Operation
Page 4-21
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