READ? Subsystem

Last updated: December 3, 2008

Syntax Diagram and Command Descriptions

Description

The READ? command provides a sequential method to make measurements and retrieve the results. READ? will hang the GPIB bus until the measurement is completed, or until the timeout value has been exceeded. Associated SETup commands (for each measurement) are used with the READ? command to retrieve desired measurement results in a sequential manner.

Sending a READ? command is equivalent to an INITiate/FETCh cycle for a measurement. A READ? command executes an abort action on that measurement followed by an INITiate and a FETCH?.

READ? commands can be mixed with FETCH? queries in order to make combinations of sequential and overlapped operations. One measurement can be issued a READ? command (sequential), and the next measurement can be issued INITiate/FETCh? commands (overlapped), if necessary.

The advantage of using the READ? commands to obtain measurement results, as opposed to the INITiate/FETCh method is:

It is simpler. Fewer commands are required to obtain measurement results.

Some disadvantages of using READ? over INITiate and FETCh are:

The test set does not process any additional GPIB commands until the requested measurement results are available.
The sequential nature of the READ? command does not allow the user to make concurrent measurements. Concurrent measurements require the overlapped commands INITiate, DONE? and FETCh? .

The READ? command does not provide measurement results such as statistics that are available using the INITiate/FETCh method.
The READ? commands have pre-defined measurement results. If additional results are needed from a measurement they may be obtained with a FETCh? query.

NOTE

Trigger arming for each measurement is controlled in the SETup subsystem. Best practice during remote operation is to set trigger arm to single (Continuous Off).

Programming Example

 
OUTPUT 714;"READ:TXPower?" !Starts TX power measurement. As soon as the
                           !measurement cycle has completed, the test set
                           !provides the TX power measurement results to the
                           !controlling application.
ENTER 714;integrity, tx_carrier_power !Enters the integity indicator and
                                      !TX carrier power measurement into
                                      !controlling application.