Keysight P9241, Scpi Programmer'S Manual

Page: 53 / 1344

Getting Started
3
Keysight P9241/42/43A Oscilloscopes SCPI Programmer's Guide 53
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 Chapter 30 , “:WAVeform Commands,” starting on page
997.
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.
NOTE
Aborting a Digitize Operation Over the Programming Interface
When using the programming interface, you can abort a digitize operation by sending a Device
Clear over the bus (for example, myScope.IO.Clear).