Sending Gpib Command Messages; Types And Structure Of Gpib Commands - Agilent Technologies 4288A Programming Manual

Sending GPIB Command Messages

Types and structure of GPIB commands

GPIB commands available with the 4288A can be divided into two groups:
4288A-specific commands
These commands are specific to the 4288A. They provide access to all measurement
features and some generic features built into the 4288A. Commands in this group have a
hierarchical (multi-level) structure called the "command tree" (see "GPIB Command Tree"
on page 203). Each command consists of multi-level strings (mnemonics) and colons (:)
that delimit the levels of the hierarchy.
IEEE common commands
These are commands that provide access to generic features defined by IEEE488.2. They
are accepted by any instrument that complies with IEEE488.2. Each command in this
group is prefixed with an asterisk (*). These commands have no hierarchical levels.
Command tree concept
The topmost command in the command tree is referred to as the "root command," or
simply the "root." To access a lower-level command in the command tree, you must
specify the appropriate path, which looks like a directory path in the DOS file system.
Turning on the power or resetting the instrument changes the current path to the root. Also,
different path settings are used depending on the special symbols contained in messages:
Message terminators
When a message terminator such as <new line> is detected, the current
path is set to the root.
Colons (:) When a colon is detected between two command mnemonics, the
current path is changed to the next lower level. When a colon is
detected at the beginning of a command, the command mnemonic that
follows is specified as the root level command.
Semicolons (;) A semicolon is used to delimit two commands contained in the same
message without changing the current path.
Figure 2-3 illustrates how colons and semicolons can be used to efficiently access various
commands in the command tree.
Chapter 2
Overview of Remote Control
Sending GPIB Command Messages
21