4-12
BIT 4886 051010
defective. If the response is PASSED, the cable is correct; remove the jumper and reconnect
the cable to the computer.
4. If the loop back connector was not available and steps 1 And 3 were completed successfully,
contact Kepco to obtain loop back connector P/N 195-0111 and rerun the test. If each of the
above steps is completed successfully, the problem lies in the computer hardware and/or
software. If the serial communication is monitored at the computer end, every DIAG:LBT?
command will cause the IDN response to be sent to the computer.
4.5.3
USING SCPI COMMANDS FOR RS 232 COMMUNICATION.
The unit must be in remote mode before RS 232 commands affecting the output can be exe-
cuted (e.g., VOLT 10;OUTP ON). This can be accomplished by sending SYST:REM ON prior to
sending any commands that affect the power supply output. (See PAR. B.87 and Figure B-7)
4.6
SCPI PROGRAMMING
SCPI (Standard Commands for Programmable Instruments) is a programming language con-
forming to the protocols and standards established by IEEE 488.2 (reference document
ANSI/
IEEE Std 488.2, IEEE Standard Codes, Formats, Protocols, and Common Commands
). SCPI com-
mands are sent to the Interface Card as output strings within the selected programming lan-
guage (PASCAL, BASIC, etc.) in accordance with the manufacturer’s requirements for the
particular GPIB interface card used.
Different programming languages (e.g., BASIC, C, PASCAL, etc.) have different ways of repre-
senting data that is to be put on the IEEE 488 bus. It is up to the programmer to determine how
to output the character sequence required for the programming language used. Address infor-
mation (GPIB address) must be included before the command sequence. (See PAR. 2.2.1 to
establish the Interface Card GPIB address.)
4.6.1
SCPI MESSAGES
There are two kinds of SCPI messages: program messages from controller to power supply,
and response messages from the power supply to the controller. Program messages consist of
one or more properly formatted commands/queries and instruct the power supply to perform an
action; the controller may send a program message at any time. Response messages consist of
formatted data; the data can contain information regarding operating parameters, power supply
state, status, or error conditions.
4.6.2
COMMON COMMANDS/QUERIES
Common commands and queries are defined by the IEEE 488.2 standard to perform overall
power supply functions (such as identification, status, or synchronization) unrelated to specific
power supply operation (such as setting voltage/current). Common commands and queries are
preceded by an asterisk (*) and are defined and explained in Appendix A. Refer also to syntax
considerations (PARs. 4.6.2 through 4.6.5).
4.6.3
SCPI SUBSYSTEM COMMAND/QUERY STRUCTURE
Subsystem commands/queries are related to specific power supply functions (such as setting
output voltage, current limit, etc.) Figure 4-5 is a tree diagram illustrating the structure of SCPI
subsystem commands used in the Interface Card with the “root” at the left side, and specific
commands forming the branches. The following paragraphs introduce the subsystems; subsys-
tem commands that are defined and explained in Appendix B.
