4 Operating the Power Supply Remotely
SCPI Command Completion
SCPI commands sent to the power supply are processed either sequentially or in parallel. Sequential commands finish execution before a subsequent command begins. Parallel commands allow other commands to begin executing while the parallel command is still executing.
The following is a list of parallel commands. You should use some form of command synchronization as discussed in this section before assuming that these commands have completed.
| OUTPut:STATe | INITiate | |
| VOLTage | OUTPut:PROTection:CLEar | |
| CURRent |
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| The *WAI, *OPC, and *OPC? common commands provide different | ||
| ways of indicating when all transmitted commands, including any | ||
| parallel ones, have completed their operations. Some practical | ||
| considerations for using these commands are as follows: | ||
*WAI | This command prevents the power supply from processing subsequent | ||
| commands until all pending operations are completed. For example, | ||
| the *WAI command can be used to make a voltage measurement after | ||
| an output on command has completed: | ||
| OUTPut ON;*WAI;:MEASure:VOLTage? | ||
*OPC? | This command places a 1 in the Output Queue when all pending | ||
| operations have completed. Because it requires your program to read | ||
| the returned value before executing the next program statement, | ||
| *OPC? can be used to cause the controller to wait for commands to | ||
| complete before proceeding with its program. | ||
*OPC | This command sets the OPC status bit when all pending operations | ||
| have completed. Since your program can read this status bit on an | ||
| interrupt basis, *OPC allows subsequent commands to be executed. | ||
| The trigger subsystem must be in the Idle state for the status OPC bit to be | ||
NOTE | |||
| true. As far as triggers are concerned, OPC is false whenever the trigger | ||
| subsystem is in the Initiated state. | ||
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| Device Clear |
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| You can send a Device Clear at any time to abort a SCPI command | ||
| that may be hanging up the GPIB interface. Device Clear clears the | ||
| input and output buffers of the power supply. The status registers, | ||
| error queue, and all configuration states are left unchanged by Device | ||
| Clear. Device Clear also prepares the power supply to accept a new | ||
| command string. The following statement shows how to send a device | ||
| clear over the GPIB interface using Agilent BASIC: | ||
| CLEAR 705 | ||
62 | Series N5700 User’s Guide |
