Fluke 9640A Series, Instruction Manual

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SCPI and IEEE Bus Descriptions
Program and Response Messages
4B
4B-9
This program message consists of two message units. The unit separator (semi-colon)
separates message units.
Basically there are two types of commands: common commands and SCPI commands.
Common Commands
The common command header starts with the asterisk character (*), for example *RST.
SCPI Commands
SCPI command headers may consist of several keywords (mnemonics), separated by the
colon character (:). An sample of the SCPI command tree structure is shown in
Figure 4B-8.
Subnodes Root Endnodes
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Figure 4B-8. The SCPI Command Tree
Each keyword in a SCPI command header represents a node in the SCPI command tree.
The leftmost keyword (AM in the previous example) is the root level keyword,
representing the highest hierarchical level in the command tree.
The keywords following represent subnodes under the root node. See the
Command Tree
section of this chapter for more details of this subject.
Forgiving Listening
The syntax specification of a command is as follows:
POWer:OFFSet <numeric value>
Where: POW and OFFS specify the shortform, and POWer and OFFSet specify the
longform. However, POWE or OFF are not allowed and cause a command error.
In program messages either the long or the shortform may be used in upper or lower case
letters. You may even mix upper and lower case. There is no semantic difference between
upper and lower case in program messages. This instrument behavior is called forgiving
listening.
For example, an application program may send the following characters over the bus:
SEND=> pOwEr:OFfSetT
1.23
The example shows the shortform used in a mix of upper and lower case
SEND=>
Power:Offs 1.23
The example shows a mix of longform and shortform and a mix of upper and lower case.
Notation Habit in Command Syntax
To clarify the difference between the forms, the shortform in a syntax specification is
shown in upper case letters and the remaining part of the longform in lower case letters.
Notice however, that this does not specify the use of upper and lower case characters in
the message that you actually sent. Upper and lower case letters, as used in syntax