Ceyear 4051 Series, Руководство пользователя

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6 Remote control
6.1 Basis of Remote Control
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4) Command tree
Special instrument commands are used in most of remote control programs. To analyze this kind of command,
the SCPI structure should be similar to the file system, known as the command tree.
The top command is the root command, referred to as the ―root‖. Follow the specific path of the tree structure
to next layer in command analysis. Example: :POWer:ALC:SOURce
？ Where, ―:POWer‖ refers to AA,
―:ALC‖ refers to BB, and ―:SOURce‖ refers to GG. The whole command path is (:AA:BB:GG).
The command interpreter, a module of the instrument software, is dedicated to analysis of each received SCPI
command. It is used to divide the command into separate command elements according to a series of rules to
distinguish command tree paths. The current command should be kept unchanged after analysis, so as to
analyze the subsequent command more rapidly and efficiently as the same command keyword may be used in
various paths. The current command path should be set as the root after the instrument is started or reset
(*RST).
5) Command parameter and response
Table 6.4 SCPI Command Parameters and Response Types
Parameter type Response Data Types
Numeric Real or integer
Extended Numeric Integer
Discrete Discrete
Boolean Numeric Boolean
String String
Block Block with definite length
Block of uncertain length
Non-decimal Numeric Hexadecimal system
Octal system
Binary system
SCPI defines different data formats for use in program and response messages. It does this to accommodate
the principle of forgiving listening and precise talking. Refer to IEEE488.2 for more information. Forgiving
listening means the command and parameter formats are flexible. For example, the signal/spectrum analyzer
is set with a frequency offset status command: FREQuency:OFFSet:STATe ON|OFF|1|0. The following
command formats are to turn on the frequency offset mode:
:FREQuency:OFFSet:STATe ON, :FREQuency:OFFSet:STATe 1,
:FREQ:OFFS:STAT ON, :FREQ:OFFS:STAT 1.
Various parameter types correspond to one or more response data type(s). The numeric type of the parameter
will change into the data type in query. Response data are accurate, strictly referred to as ―accurate telling‖.
For example, if you query the power status (:POWer:ALC:STATe?) when it is on, the response is always 1,
regardless of whether you previously sent :POWer:ALC:STATe1 or :POWer:ALC:STATe ON.
a) Numerical parameter
Special instrument commands and general commands can be expressed as numeric parameters. All kinds of
common decimal counting can be applied for reception of numeric parameters, including the plus or minus,
decimal and scientific counting methods. If one device can only receive the specific numeric type, such as the
integer, the received numeric parameter will be automatically rounded.