Standard Commands for Programmable Instruments
Standard Commands for Programmable Instruments ( SCPI ; German standard commands for programmable instruments ) is a standardized set of commands that is used to control and program measuring devices . The commands are often referred to as "skippy" commands. The underlying physical communication layer is not prescribed by SCPI. The data can be transmitted via various bus systems such as GPIB , RS232 , USB , VXI or LXI .
The SCPI commands are transmitted in the form of ASCII text and can be generated in any programming language in any development environment. However, access from the programming language to the respective bus system must be available in order to be able to send the commands and receive results.
The first standardization took place in 1987 as part of the IEEE 488.2-1987 standard. Among other things, this laid down a number of basic management commands for devices with a GPIB bus. They all start with a '*'. SCPI took over, generalized and expanded them. SCPI was standardized for the first time in 1992 and has been expanded and improved occasionally since then, the last time in 1999. Both the basic structure of SCPI commands, various general commands and the commands for some special classes of devices are standardized.
The reason for the introduction of SCPI was the uncontrolled growth of commands despite IEEE 488.2 at the various measuring device manufacturers and the resulting effort for training and device replacement. However, the SCPI standard does not prevent manufacturers of modern devices from implementing a large number of their own commands that correspond to SCPI in terms of structure, but go far beyond the standardized commands for the corresponding device classes. As long as the commands basically correspond to the structure of SCPI commands, these are also referred to as SCPI commands.
With a very high probability, one can only rely on the fact that the command is *IDN?present on a device with SCPI or SCPI-like commands . This asks for the manufacturer, model number, serial number and software version of a device. Although this command and the response are standardized, there are devices that respond to *IDN?with an unstandardized response. In general, however, the answer is sufficient to at least identify the type of device and thus the command set that it understands.
Examples
- The command
SYSTem:COMMunicate:SERial:BAUD 2400can be used to set the baud rate of an RS232 interface to 2400 bit / s. The command can beSYST:COMM:SER:BAUD 2400abbreviated to. - The command
SYSTem:COMMunicate:SERial:BAUD?can be used to query the currently set baud rate of an RS232 interface. The command can beSYST:COMM:SER:BAUD?abbreviated to.
Weblinks & references
- ↑ SCPI specification from 1999 (PDF, English; 4.2 MB)