Multiple Commands In A Message; Moving Among Subsystems; Including Common Commands - Keysight Technologies N3301A Programming Manual

2 - Introduction to Programming

Multiple Commands in a Message

Multiple SCPI commands can be combined and sent as a single message with one message terminator.
There are two important considerations when sending several commands within a single message:
♦ Use a semicolon to separate commands within a message.
♦ There is an implied header path that affects how commands are interpreted by the electronic
load.
The header path can be thought of as a string that gets inserted before each command within a
message. For the first command in a message, the header path is a null string. For each subsequent
command the header path is defined as the characters that make up the headers of the previous
command in the message up to and including the last colon separator. An example of a message with
two commands is:
CURR:LEV 3;PROT:STAT OFF
which shows the use of the semicolon separating the two commands, and also illustrates the header path
concept. Note that with the second command, the leading header "CURR" was omitted because after the
"CURR:LEV 3" command, the header path became defined as "CURR" and thus the instrument
interpreted the second command as:
CURR:PROT:STAT OFF
In fact, it would have been syntactically incorrect to include the "CURR" explicitly in the second
command, since the result after combining it with the header path would be:
CURR:CURR:PROT:STAT OFF
which is incorrect.

Moving Among Subsystems

In order to combine commands from different subsystems, you need to be able to reset the header path
to a null string within a message. You do this by beginning the command with a colon (:), which discards
any previous header path. For example, you could clear the output protection and check the status of the
Operation Condition register in one message by using a root specifier as follows:
OUTPut:PROTection:CLEAr;:STATus:OPERation:CONDition?
The following message shows how to combine commands from different subsystems as well as within the
same subsystem:
VOLTage:LEVel 20;PROTection 28; :CURRent:LEVel 3;PROTection:STATe ON
Note the use of the optional header LEVel to maintain the correct path within the voltage and current
subsystems, and the use of the root specifier to move between subsystems.

Including Common Commands

You can combine common commands with subsystem commands in the same message. Treat the
common command as a message unit by separating it with a semicolon (the message unit separator).
Common commands do not affect the header path; you may insert them anywhere in the message.
VOLTage:TRIGgered 17.5;:INITialize;*TRG
OUTPut OFF;*RCL 2;OUTPut ON
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