GPIB Operation 6-11
Command path rules
• Each new program message must begin with the root command, unless it is optional (e.g.,
[:SOURce]). If the root is optional, treat a command word on the next level as the root.
• The colon (:) at the beginning of a program message is optional and need not be used.
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 separate com-
mands 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 be moved 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 command
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 program message must be terminated:
:outp on <PMT>
Command execution rules
• Commands execute in the order that they are presented in the program message.
• An invalid command generates an error and is not executed.
• Valid commands that precede an invalid command in a multiple command program
message are executed.
• Valid commands that follow an invalid command in a multiple command program message
are ignored.
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