Agilent Technologies 54621A Programmer's Manual page 56

Programming and Documentation Conventions
The Command Tree
Subsystem Commands
Subsystem commands are grouped together under a common node of the
command tree, such as the TIMEBASE commands. Only one subsystem may be
selected at any given time. When the instrument is initially turned on, the
command parser is set to the root of the command tree, therefore, no subsystem
is selected.
Tree Traversal Rules
Command headers are created by traversing down the command tree. A legal
command header from the command tree would be :CHANNEL1:RANGE. This
is called a compound header. A compound header is a header made of two or
more mnemonics separated by colons. The mnemonic created contains no
spaces. The following rules apply to traversing the tree:
• A leading colon or a <program message terminator> (either an <NL> or EOI
true on the last byte) places the parser at the root of the command tree. A
leading colon is a colon that is the first character of a program header.
• Executing a subsystem command places you in that subsystem until a leading
colon or a <program message terminator> is found. In the Command Tree,
use the last mnemonic in the compound header as a reference point (for
example, RANGE). Then find the last colon above that mnemonic
(CHANNEL<n>). That is the point where the parser resides. Any command
below that point can be sent within the current program message without
sending the mnemonics that appear above them (for example, OFFSET).
Examples
The OUTPUT statements in the examples are written using HPBASIC 6.3. The
quoted string is placed on the bus, followed by a carriage return and linefeed
(CRLF).
Example 1:
OUTPUT 707;":CHANNEL1:RANGE 0.5 ;OFFSET 0"
The colon between CHANNEL1 and RANGE is necessary because
CHANNEL1:RANGE is a compound command. The semicolon between the
RANGE command and the OFFSET command is the required program message
unit separator. The OFFSET command does not need CHANNEL1 preceding
it, since the CHANNEL1:RANGE command sets the parser to the CHANNEL1
node in the tree.
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