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Section 11: Remote operations
Multiple command messages
Multiple commands can be sent in the same program message if they are separated by semicolons
(;). Example showing two commands in one program message:
:stat:pres; :stat:oper:enab <NRf>
When the above message 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>; ptr <NRf>; ntr <NRf>
After the first command (:enab) is executed, the path pointer is at the third command level in the
structure. Since :ptr and :ntr are also on the third level, they can be typed in without repeating
the entire path name. Notice that the leading colon for :ptr and :ntr are not included in the
program message. If a colon were included, the path pointer would reset to the root level and expect
a root command; because :ptr and :ntr are not root commands, an error would occur.
Command path rules
1. Each new program message must begin with the root command, unless it is optional (for
example, [:SENSe]). If the root is optional, simply treat a command word on the next level as the
root.
2. The colon (:) at the beginning of a program message is optional and need not be used. Example:
:stat:pres = stat:pres
3. 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 commands within the
program message (see next rule).
4. When the path pointer detects a colon (:) that immediately follows a semicolon (;), it resets back
to the root level.
5. The path pointer can only move down. It cannot be moved up a level. Executing a command at a
higher level requires that you start over at the root command.
Combining common and SCPI commands
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
does not affect the path pointer. Example:
:stat:oper:enab <NRf>; ptr <NRf>; *ESE <NRf>; ntr <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 hangs if your computer does not provide this termination. The following example shows
how a multiple command program message must be terminated:
:rout:open all; scan (@1:5) <PMT>
11-14
Model 6517B Electrometer Reference Manual
6517B-901-01 Rev. C / August 2015
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