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2 Programming Overview
Controller Interface
The physical interface is the RJ-45 connection on the instrument for 10BASE-T.
Data transfer takes place over Ethernet using TCP/IP and the VXI-11 protocol. In order
to communicate with the instrument the PC must have a VXI-11 client implementation
either as part of the controller program or using a third party software package on the
controlling PC. The examples in Appendix A of this manual are written using National
Instruments’ NI-VISA™ product.
Command Structure
Format
The Master™ product line implements a remote interface based on the 1999 SCPI
Standard. This is an ASCII-based command set.
Some basic details are described below. For a more detailed description see the SCPI
Standard, available for download on the SCPI Consortium website.
Command Tree
SCPI commands are organized in a “tree” structure. The base of the tree is called the
“root”. The “branches” are the functional subsystems. Each “branch” can have sub-
branches. The final node is called the “leaf”. The entire sequence of branches, plus the
leaf, make up the command. For example, part of the “SENSe” branch looks like this:
[:SENSE]
:FREQuency
:CENTer
:STARt
:STOP
:SPAN
:FULL
:PREVious
Although they are at different levels in the tree, “CENTer” and “FULL” are both leaves
on the tree.
There can be branches and leaves in the tree with the same name as long as they appear at
different levels. For example, there is an “AUTO” leaf at the tip of both of these
branches:
[:SENSe]
:BANDwidth
:RESolution
:AUTO
[:SENSe]
:BANDwidth
:VIDeo
:AUTO
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