HP 8360 User Manual

Page 98

root

level 1

c c

level 2 EE FF GG

Figure

A Simplified Command Tree

In the command tree shown in Figure

the command closest to

the top is the

root command,

or simply the

root.

Notice that you

must follow a particular

path

to reach lower level subcommands. For

example, if you wish to access the GG command, you must follow the
path AA to BB to GG.

Paths Through the Command Tree

To access commands in different paths in the command tree, you
must understand how an instrument interprets commands. A special
part of the instrument firmware, a

purser,

decodes each message sent

to the instrument. The parser breaks up the message into component
commands using a set of rules to determine the command tree path
used. The parser keeps track of the

current path,

the level in the

command tree where it expects to find the next command you send.
This is important because the same keyword may appear in different
paths. The particular path you use determines how the keyword is
interpreted. The following rules are used by the parser:

Power On and Reset

After power is cycled or after

the current path is set to the

root.

Message Terminators

A message terminator, such as a character, sets the
current path to the root. Many programming languages have
output statements that send message terminators automatically.
The paragraph titled, “Details of Commands and Responses,”
discusses message terminators in more detail.

Colon

When it is between two command mnemonics, a colon moves the
current path down one level in the command tree. For example,
the colon in MEAS:VOLT specifies that VOLT is one level below
When the colon is the first character of a command, it specifies
that the next command mnemonic is a root level command. For
example, the colon in :

specifies that

is a root level

command.

Getting Started Programming