64 Chapter2
Programming Fundamentals
SCPI Language Basics
Parameters in Commands
There are four basic types of parameters: booleans, keywords, variables
and arbitrary block program data.
ON|OFF|0|1 This is a two state boolean-type parameter. The
numeric value 0 is equivalent to OFF. Any numeric
value other than 0 is equivalent to ON. The numeric
values of 0 or 1 are commonly used in the command
instead of OFF or ON. Queries of the parameter always
return a numeric value of 0 or 1.
keyword The keywords that are allowed for a particular
command are defined in the command syntax
description.
Units Numeric variables may include units. The valid units
for a command depend on the variable type being used.
See the following variable descriptions. The indicated
default units will be used if no units are sent. Units can
follow the numerical value with, or without, a space.
Variable A variable can be entered in exponential format as well
as standard numeric format. The appropriate range of
the variable and its optional units are defined in the
command description.
The following keywords may also be used in commands,
but not all commands allow keyword variables.
DEFault - resets the parameter to its default value.
UP - increments the parameter.
DOWN - decrements the parameter.
The numeric value associated with DEFault can be
queried by adding the keyword to the command in its
query form. The keyword must be entered following the
question mark.
Example query: SENSE:FREQ:CENTER? DEFAULT
Variable Parameters
<freq>
<bandwidth> A frequency parameter is a positive rational number
followed by optional units. The default unit is Hz.
Acceptable units include: HZ, KHZ, MHZ, GHZ.
<time>
<seconds> A time parameter is a rational number followed by
optional units. The default units are seconds.
Acceptable units include: S, MS, US.
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