Queryusage - HP 1652B Programming Reference Manual

Note
Introduction to Programming an Instrument
1-6
Command headers immediately followed by a question mark (?) are
queries. After receiving a query, the instrument interrogates the
requested function and places the response in its output queue. The
output message remains in the queue until it is read or another command
is issued. When read, the message is transmitted across the bus to the
designated listener (typically a controller). For example, the logic
analyzer query :MACHINEl:TWAVEFORM:RANGE? places the
current seconds per division full scale range for machine 1 in the output
queue. In BASIC, the input statement
ENTER XXX; Range
passes the value across the bus to the controller and places it in the
variable Range.
Query commands are used to find out how the instrument is currently
configured. They are also used to get results of measurements made by
the instrument. For example, the command
instructs the instrument to place the X to 0 time in the output queue.
The output queue must be read before the next program message is sent.
For example, when you send the query :TWAVEFORM:XOTIME? you
must follow that with an input statement. In BASIC, this is usually done
with an ENTER statement.
Sending another command before reading the result of the query will
cause the output buffer to be cleared and the current response to be lost.
This will also generate a "QUERY UNTERMINATED" error in the
error queue.
HP 1662Bll663B
Programming Reference