B&K Precision 4079 - Manual - Manual (Page 47)

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The Program Message Unit Separator consists of a semicolon (';'), optionally preceded and/or followed by whitespace
characters. A whitespace character is defined as the ASCII characters in the ranges 00H-09H, and 0BH-20H. This range
includes the ASCII control characters and the space, but excludes the Linefeed character.
The Program Message Terminator consists of optional whitespace characters, followed by one of three options:
a) The Linefeed (LF) character (ASCII 0A);
b) The GPIB EOI bus line being set true on the last byte of the message;
c) LF being sent with EOI true.
The Program Message Unit can be divided into three sections as follows:
a) Program Header
The Program Header represents the operation to be performed, and consists of ASCII character mnemonics. Two types of
Program Headers are used in the 4076 & 4079: Instrument-control headers and Common Command and Query headers. A
Program Header may consist of more than one mnemonic, in which case the mnemonics are separated from each other by the
colon (':'). For instrument control commands, the mnemonics are specified by the SCPI standard, and indicate the tree
structure of the command set. The first mnemonic indicates the subsystem being controlled. Common Command and Query
Program Headers consist of a single mnemonic prefixed by an asterisk ('*').
The mnemonics consist of upper - or lower-case alpha characters. Mnemonics may be written in either the long form, in
which the entire mnemonic is written out, or the short form, in which only a specified portion of the mnemonic is written out.
Some mnemonics have only one form due to their short length. Where a command is described, the portion appearing in
upper case is the short form. Only the short form or the long form may be used.
Example: The command to set the frequency to 1KHz may be written in the following ways:
SOURCE:FREQUENCY 1KHZ
SOUR:FREQ 1KHZ
SOURCE:FREQ 1KHZ
Some mnemonics in a specified Program Header may be optional. This is indicated in the command description by the
mnemonic being enclosed in square brackets ([...]). This means it is not necessary to write the mnemonic into the Program
Header: it is a default condition. The 'SOURCE' mnemonic, for example, is optional. Not specifying it will cause the device
to search for the mnemonics in the Program Header under the Source Subsystem. For example, the frequency may be set by
the commands
FREQ:CW 1KHz
FREQ 1KHz
since the 'CW' mnemonic is also optional.
b) Program Header Separator
The Program Header Separator is used to separate the program header from the program data. It consists of one or more
whitespace characters, denoted as <ws>. Typically, it is a space.
c) Program Data
The Program Data represent the values of the parameters being set, for example, the '1KHZ' in the above
examples. Different forms of program data are accepted, depending on the command. The Program Data types used in the
instrument are:
i) Character program data
This form of data is comprised of a mnemonic made up of lower - or upper-case alpha characters. As with Program Header