3-44 BOP HIPWR 111315Refer to Table 2-11 for input/output signal allocations for communication via the GPIB, Table 2-5for RS 232, and Table 2-2 for the BITBUS. All power supply functions available from the keypadcan be programmed via remote SCPI commands. In addition, some features that are not avail-able from the keypad may be implemented using remote commands (see PAR. 3.5.1).This section includes a discussion of GPIB bus protocols (PAR. 3.5), instructions for changingthe GPIB address (PAR. 3.5.3.1.1), a discussion of the VISA (Virtual Instrumentation SoftwareArchitecture) driver supplied with the unit (PAR. 3.5.5), RS 232C Operation (PAR. 3.5.6), fol-lowed by a detailed explanation of SCPI programming (PAR. 3.6).3.5.1 OPERATING FEATURES AVAILABLE ONLY BY REMOTE COMMANDSThe following paragraphs describe features of the BOP that are not available from the frontpanel, but can be implemented using remote commands.3.5.1.1 EXPANDED WAVEFORMS AND PROGRAMSRefer to the documentation supplied with the VISA driver included with the BOP for moredetailed information regarding waveforms and programs, including examples of how to create atable to load the variables.3.5.2 PROGRAMMING TECHNIQUES TO OPTIMIZE PERFORMANCE3.5.2.1 PROGRAMMING VOLTAGE/CURRENT LIMIT AND CURRENT/VOLTAGE LIMITKepco's auto-crossover digital supplies can operate in either voltage mode with current limit, orcurrent mode with voltage limit. The operating mode is determined by the voltage and currentcommands received, as well as the load. Each time voltage and current commands arereceived, the unit must evaluate the commands and the load conditions to determine the neces-sary operating mode. Reducing the number of times this evaluation must be made is desirablebecause Kepco's digital auto-crossover supplies employ two separate feedback loops. Eachtime there is a potential mode change, there is always an uncontrolled period of a few millisec-onds while the two feedback loops compete for control of the output. By changing only theactive parameter (e.g., voltage for voltage mode), there is no doubt as to what the operatingmode will be, so the unit is never uncontrolled, response is quick and no transients are possible.Recommended programming techniques are:1. Minimize programmed mode (voltage or current) changes. Unless absolutely required by thetest parameters, allow the power supply to automatically switch modes as determined by theload. This will improve response time and reduce undesirable transients.2. Once the mode (voltage or current) is programmed, program the active parameter to zeroand the complementary limit parameter to the maximum anticipated for application. Thenprogram only the active parameter. The active parameter is the parameter that controls theoutput, e.g., voltage controls the output in voltage mode.3. Never program both the active and complementary limit parameter to zero. This can result inlong response times. Set the active parameter to zero and the complementary limit parame-ter to a minimum, e.g., 10% of maximum, to ensure that the active mode is defined.
