3-54 BOP HIPWR 0319123.5.6.4 ISOLATING RS 232 COMMUNICATION PROBLEMSA Loop Back test can be run from the front panel to aid in isolating RS 232 communication prob-lems. The unit is designed to pass the test only with the Loop Back test connector (part of Kit219-0436, see Table 1-5) installed.1. From the power-up screen press % key to enter the General Setup menu, then highlightRevisions/TEST. press ! to enter the Test Subsystem menu.2. Highlight Serial Interface and press # to run the test with the Loop Back Test connectorNOT installed and verify the LCD reads Failed. If the LCD reads Passed, the power supplyis defective and requires repair.3. Install the loop back test connector into RS 232 port and press the # key to rerun the test.If the LCD reads Passed, the power supply is operating properly. If the LCD reads Failed,the unit requires repair.4. To test the integrity of the cable assembly connecting the power supply RS 232 port to thecomputer, remove the Loop Back test connector from the power supply RS 232 port andconnect the cable in its place. With the DB9 adapter installed on the opposite end of thecable, connect a short jumper wire between pins 2 and 3 of the adapter connector andrepeat the test of step 3 above. If the LCD display reads Failed, the cord is either theimproper type (not null modem) or is defective. If the LCD display reads Passed, the cable iscorrect; remove the jumper and reconnect the cable to the computer.If each of the above steps is completed successfully, the problem lies in the computer hard-ware and/or software. Refer to the Product Support area of the Kepco website for additionalinformation regarding RS 232 communications problems: www.kepcopower.com/support.3.6 SCPI PROGRAMMINGSCPI (Standard Commands for Programmable Instruments) is a programming language con-forming to the protocols and standards established by IEEE 488.2 (reference documentANSI/IEEE Std 488.2, IEEE Standard Codes, Formats, Protocols, and Common Commands). SCPIcommands are sent to the BOP Power Supply as ASCII output strings within the selected pro-gramming language (PASCAL, BASIC, etc.) in accordance with the manufacturer’s require-ments for the particular GPIB controller 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 howto output the character sequence required for the programming language used. Address infor-mation (GPIB address) must be included before the command sequence. (See PAR.3.5.3.1.1 toestablish the BOP Power Supply GPIB address.)3.6.1 SCPI MESSAGESThere 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 ofone or more properly formatted commands/queries and instruct the power supply to perform anaction; the controller may send a program message at any time. Response messages consist offormatted data; the data can contain information regarding operating parameters, power supplystate, status, or error conditions.
