3-44 BOP HIPWR 0319121. 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.3.5.2.2 MAKING SURE THE PREVIOUS COMMAND IS COMPLETESome SCPI commands require a flash memory update and can take an indeterminate amountof time to complete. These commands are:• *SAV• MEM:PACK• MEM:UPD• CAL:COPY• CAL:SAVE• SYST:PASS:NEW• SYST:SEC:IMMWhen sending these commands via the GPIB, these commands require a query to be added tothe command string to verify the previous command is complete. When the command is com-plete, the unit updates the status byte and indicates MAV (Message Available, bit 4 - see TableA-3) is true. MAV indicates that there is a response to be received by the computer, so when itbecomes set, the unit is ready for its next command after reading back the data from the querythat was added to the command string.When sending the above commands via the RS 232 bus, data flow control must be enabled(XON) for the unit to properly update flash memory.The *OPC? query is ideal to check if the previous command is complete since it returns either a1 or 0. It is important that it be sent as a part of the same string as the command that causes aflash update. As an example, sending CAL:SAVE 12/31/2005;:*opc? or *opc?;:CAL:SAVE12/31/2005 are valid command strings. Sensing the commands separately will not verify that theprevious command is complete. Figure 3-16 is a program written in C, incorporating these tech-niques.Failure to provide an adequate delay can result in:• Commands that are not processed,• The following command may be received in error, causing an error in the transmission,• Unit lock-up requiring power cycling of the unit. If working via the GPIB bus, sendingInterface Clear and Device Clear followed by *RST will unlock the unit.
