Reading Query Responses From The Oscilloscope - Agilent Technologies InfiniiVision 7000A Series Programmer's Manual

3
Getting Started
The easiest method of transferring a digitized waveform depends on data
structures, formatting available and I/O capabilities. You must scale the
integers to determine the voltage value of each point. These integers are
passed starting with the left most point on the instrument's display.
For more information, see the waveform subsystem commands and
corresponding program code examples in ":WAVeform Commands" on
page 616.
Aborting a Digitize Operation Over the Programming Interface
N O T E
When using the programming interface, you can abort a digitize operation by sending a
Device Clear over the bus (for example, myScope.IO.Clear).

Reading Query Responses from the Oscilloscope

After receiving a query (command header followed by a question mark),
the instrument interrogates the requested function and places the answer
in its output queue. The answer remains in the output queue until it is
read or another command is issued. When read, the answer is transmitted
across the interface to the designated listener (typically a controller).
The statement for reading a query response message from an instrument's
output queue typically has a format specification for handling the response
message.
When using the VISA COM library in Visual Basic, you use different read
methods (ReadString, ReadNumber, ReadList, or ReadIEEEBlock) for the
various query response formats. For example, to read the result of the
query command :CHANnel1:COUPling? you would execute the statements:
myScope.WriteString ":CHANnel1:COUPling?"
Dim strQueryResult As String
strQueryResult = myScope.ReadString
This reads the current setting for the channel one coupling into the string
variable strQueryResult.
All results for queries (sent in one program message) must be read before
another program message is sent.
Sending another command before reading the result of the query clears
the output buffer and the current response. This also causes an error to
be placed in the error queue.
Executing a read statement before sending a query causes the controller to
wait indefinitely.
The format specification for handling response messages depends on the
programming language.
Agilent InfiniiVision 7000A Series Oscilloscopes Programmer's Guide 53