Wayne 4310 - Figure 5-1 GPIB Message Structure; Figure 5-2 GPIB Command Structure

REMOTE CONTROL (GPIB & RS-232) 5–3
5.2.4.1 Message structure
Messages are sent to the instrument as ASCII character strings. The structure of these strings
can be seen in Figure 5-1. When interpreting the strings the instrument is not case-sensitive.
Figure 5-1 GPIB Message Structure
The path command prefix allows access to commands in the SCPI command tree. Using this
approach greatly simplifies GPIB programming by allowing related commands to be grouped
together. The next part of the string is the command itself which has the structure shown in
Figure 5-2. Multiple commands can be sent in one message by separating them with a
semicolon (maximum length 256 bytes). The terminator indicates the end of the command
string to the instrument: this can be the sending of the line-feed character (ASCII 0Ah) and/or
the assertion of the EOI handshake line on the GPIB bus.
Figure 5-2 GPIB Command Structure
Each instrument command begins with a mnemonic that describes the required action, e.g.
FREQ for changing the frequency.
If the command requires a parameter, then the next character should be a white space character
(ASCII 20h), although any character in the range 00h-20h can be used with the exception of
line-feed (ASCII 0Ah).
The parameter itself can take one of three forms depending on the command:
1) Discrete data
This includes words like ON, OFF and ABS.
2) Real Number
A floating point number that can be in engineering format or a number with a multiplier
suffix K (kilo-), M (mega-) or G (giga-).
For example:
FREQ 1000.0
FREQ 1E+3