Command Sequence And Synchronization; Preventing Overlapping Execution - R&S SGT100A User Manual

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R&S SGT100A
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Numeric values are output without a unit. Physical quantities are referred to the
basic units or to the units set using the Unit command. The response 3.5E9 in
the previous example stands for 3.5 GHz.
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Truth values (Boolean values) are returned as 0 (for OFF) and 1 (for ON).
Example:
Setting command: HCOPy:DEV:COL ON
Query: HCOPy:DEV:COL?
Response: 1
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Text (character data) is returned in a short form.
Example:
Setting command: HCOPy:PAGE:ORIentation LANDscape
Query: HCOP:PAGE:ORI?
Response: LAND

15.1.4 Command Sequence and Synchronization

IEEE 488.2 defines a distinction between overlapped and sequential commands:
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A sequential command is one which finishes executing before the next command
starts executing. Commands that are processed quickly are usually implemented
as sequential commands. Sequential commands are not implemented in the instru-
ment, however the execution time of most commands is so short that they act as
sequential commands when sent in different command lines.
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An overlapping command is one which does not automatically finish executing
before the next command starts executing. Usually, overlapping commands take
longer to process and allow the program to do other tasks while being executed. If
overlapping commands do have to be executed in a defined order, e.g. in order to
avoid wrong measurement results, they must be serviced sequentially. This is
called synchronization between the controller and the instrument.
Setting commands within one command line, even though they may be implemented
as sequential commands, are not necessarily serviced in the order in which they have
been received. In order to make sure that commands are actually carried out in a cer-
tain order, each command must be sent in a separate command line.
As a general rule, send commands and queries in different program messages.
15.1.4.1

Preventing Overlapping Execution

To prevent an overlapping execution of commands, one of the commands *OPC,
*OPC? or *WAI can be used. All three commands cause a certain action only to be
carried out after the hardware has been set. The controller can be forced to wait for the
corresponding action to occur.
User Manual 1176.8674.02 ─ 07
Annex
Remote Control Basics
535