Keithley 2790, Справочное руководство

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Model 2790 SourceMeter Switch System Reference Manual 10-15
When the above is sent, the first command word is recognized as the root command (stat).
When the next colon is detected, the path pointer moves down to the next command level
and executes the command. When the path pointer sees the colon after the semicolon (;), it
resets back to the root level and starts over.
Commands that are on the same command level can be executed without having to retype
the entire command path. Example:
stat:oper:enab <NRf>; enab?
After the first command (:enab) is executed, the path pointer is at the third command level
in the structure. Since :enab? is also on the third level, it can be typed in without repeating
the entire path name. Notice that the leading colon for :enab? is not included in the pro-
gram message. If a colon were included, the path pointer would reset to the root level and
expect a root command. Since :enab? is not a root command, an error would occur.
Command path rules
• Each new program message must begin with the root command, unless it is
optional (e.g., [SENSe]). If the root is optional, simply treat a command word on
the next level as the root. For fastest operation, do not send optional data.
• A colon (:) can be used at the beginning of a program message. However, using the
colon slows down execution time. Example:
stat:pres = :stat:pres
• When the path pointer detects a colon (:) it moves down to the next command level.
An exception is when the path pointer detects a semicolon (;), which is used to sep-
arate commands within the program message (see next rule).
• When the path pointer detects a colon (:) that immediately follows a semicolon (;),
it resets back to the root level.
• The path pointer can only move down. It cannot move up a level. Executing a com-
mand at a higher level requires that you start over at the root command.
Using common and SCPI commands in the same message
Both common commands and SCPI commands can be used in the same message as long
as they are separated by semicolons (;). A common command can be executed at any com-
mand level and will not affect the path pointer. Example:
stat:oper:enab <NRf>; *ESE <NRf>
Program message terminator (PMT)
Each program message must be terminated with an LF (line feed), EOI (end or identify),
or an LF+EOI. The bus will hang if your computer does not provide this termination. The
following example shows how a multiple command program message must be terminated:
outp on <PMT>