Summary: The following are the rules for negotiating the command hierarchy
On power-up or reset, the current path is set to the root.
Message terminator, line-feed (ASCII 0Ah) or EOI, sets the current path to the root.
When a colon is the first character of a command, it specifies that the next command
mnemonic is a root level command.
When a colon is placed between two path mnemonics, the current path is moved down one
level in the command tree if the path name is valid.
A semicolon separates two commands in the same message without changing the current
path.
If a command requires more than one parameter, the separate adjacent parameters must be
specified using a comma. Commas do not affect the current path.
Common commands, such as *RST, *RCL, are not part of the tree. An instrument interprets
them in the same way, regardless of the current path setting.
Other syntax rules
Commands will be executed in the order in which they appear in the string.
A command string can contain any number of ‘query commands’: the response will contain
the replies to each query separated by a semicolon.
Only commands available in the selected mode will be accepted. Otherwise, an Execution
Error will be generated. For example, AC frequency cannot be set if Rdc type of test is
selected
Either full or abbreviated forms of the device specific commands will be accepted. The
abbreviated form is indicated by upper case letters in section 0.
Device specific commands have the same effect as pressing the equivalent front panel key
and can be expected to interact with any other instrument settings in the same way.
6.1.5 Data Output
6.1.5.1 Output Syntax
For each query which generates an output response, a Response Message Unit (RMU), will be
generated. This consists of a string of numbers or alphanumeric characters; if more than one
RMU is generated they will be delimited with a semicolon. The terminator, line-feed and EOI
asserted indicates the end of data output. All characters will be upper case.
Figure 6-3 GPIB Data Output
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