Measurement Control Commands and States

Measurement control commands are used to switch over between the following four measurement states:

OFF	measurement is switched off, no results available (after `STOP`)
RUN	measurement is running
STOP	measurement has been stopped, valid results are preserved
STEP	measurement has been interrupted after a statistics cycle (in repetition mode Continuous or Counting with Stepping mode set in addition). The next cycle must be launched with a `CONTinue` command.

The STOP state corresponds to the HLT state indicated next to the softkeys controlling a measurement in manual operation. A STEP state is not defined in manual control.

The three measurement states OFF, STOP, and STEP can be mapped onto the standard SCPI state IDLE, the RUN state can be mapped onto the SCPI state INITiated. This and the relation between control commands and measurement states is shown in the following diagram:

Measurement states and control commands

The measurement control commands are supplemented by the measurement object, i.e.:

`INITiate:<meas_obj>`	Starts a measurement in the repetition mode set via the `CONFigure:<meas_obj>:CONTrol:REPetition` command (single shot, continuous or counting mode, see section Measurement Statistics). The command resets the counters for the evaluation period and statistics (the latter is not used in RF measurements) to zero, furthermore, all measurement values are set invalid (INV). As illustrated in the figure above, `INITiate` can be called in any measurement state. If the measurement is already running (RUN), `INITiate` aborts `(ABORt)` and restarts a running measurement. The measurement reserves all necessary hardware resources and switches into the RUN state. If the measurement can not be started due to a resource conflict it remains in the OFF state, and the measurement status returned by the `FETCh:<meas_obj>:STATus?` is ERR. At the same time the SCPI error -213, Init ignored, is generated.

Possible resources conflicts	The RF connector is already allocated by another measurement or signal generator. The other measurement must be switched off first. Due to the method used for the analysis, two measurements can not be evaluated at the same time.

Overlapping execution	`INITiate` is implemented as an overlapped command. In contrast to SCPI specifications, the `OPC` command (see Common Commands) can not be applied together with the `INITiate`command. The operation complete* bit (bit no. 0 in the event status register, ESR) is set immediately after the command sequence `INIT; *OPC`, i.e. as soon as the measurement is started and not after the end of the first evaluation period.

	The command `CONFigure:<meas_obj>:EREPorting <Event>, <Mode>` represents a more flexible tool for generating a service request or setting the operation complete bit after the end of a measurement (see section Event Reporting ).

`READ` command	Instead of `INITiate`, the `READ` command can be used to initiate a (single shot) measurement, see section Retrieving Measurement Results.

`ABORt:<meas_obj>`	Aborts the current measurement immediately and switches over to the OFF state. All measurement values are set invalid (INV); the hardware resources are released for other measurements. As illustrated in the figure above, `ABORt` can be called in any measurement state.

Sequential execution	`ABORt` is implemented as a sequential command. This means that `ABORt` is not complete until the measurement has released all resources and has changed to the OFF state.

`STOP:<meas_obj>`	Stops (halts) the measurement as quickly as possible; i.e. after the end of the current evaluation period (or statistics cycle, if cycles comprising several evaluation periods are defined). The measurement changes to the STOP state such that all corresponding measurement values are kept unchanged. The hardware resources are retained. As illustrated in the figure above, `STOP` can be called in the measurement states RUN and STEP. If called in the OFF state the command causes an SCPI error -221, Settings conflict.

Sequential execution	`STOP` is implemented as a sequential command. Execution of `STOP` is considered as complete as soon as the measurement state STOP is reached. The `STOP` command causes no events which are set by the event reporting system (see section Event Reporting). This means that a service request must be explicitly requested by an `*OPC` command.

`CONTinue:<meas_obj>`	Resumes the measurement for the next measurement evaluation period and changes to the RUN state. As illustrated in the figure above, `CONTinue` can be called in the measurement states STOP and STEP. If the previous measurement has been terminated (the measurement status returned by the `FETCh:<meas_obj>:STATus?` is RDY), `CONTinue`restarts the measurement and resets the counters for the evaluation period and statistics (the latter is not used for RF measurements) to zero. In the other measurement states the command causes an SCPI error -221, Settings conflict.

Overlapping execution	`CONTinue` is implemented as an overlapping command like `INITiate`. As a consequence, `*OPC` can not be used together with `CONTinue`.

Stepping mode	The stepping mode determines whether a measurement in the counting or continuous mode (see section Measurement Statistics) is interrupted after each evaluation period (or each statistics cycle, if cycles comprising several evaluation periods are defined) or not. This mode is set via the `<Stepmode>` parameter of the `CONFigure:<meas_obj>:CONTrol:REPetition CONTinuous \|` `1 ... 10000, <StopCondition>, <Stepmode>` command:

	<Stepmode> = STEP The measurement is interrupted ( measurement state STEP) after each evaluation period, and the event reporting system (see Event Reporting ) is invoked. The next measurement cycle must be started with the CONTinue:<meas_object> command.

	<Stepmode> = NONE The measurement runs according to its repetition mode. Event reporting is invoked only when the measurement stops (status = RDY).
	Note: STEP can be set in all repetition modes (single shot, continuous, counting). For a single shot measurement which is always stopped after one evaluation period, the stepping mode has no effect.

In function group RF Non Signalling, <meas_obj> can stand for any of the measurement objects POWer and SPECtrum.

Note: Some measurements rely upon the same system resources and cannot be performed simultaneously. The R&S CMU provides a mechanism to decide whether conflicting measurements are persistent or releasable; see section Task Priority Management.