Model 7002Switch System Instruction Manual - Advanced Test ...

IEEE-488 Reference5.10.7 *OPC? ⎯ operation complete queryPurposePlace a “1” in the Output Queue after all overlapped commands are completed.Format*OPC?DescriptionOn power-up, or when *CLS or *RST is executed, the Model 7002 goes into the OperationComplete Command Query Idle State (OQIS). In this state there are no pending overlappedcommands. There are three overlapped commands used by the Model 7002::INITiate:INITiate:CONTinuous ON*TRGWhen the *OPC? command is sent, the Model 7002 exits from OQIS and enters the OperationComplete Command Active State (OQAS). In OQAS, the instrument continuously monitors theNo-Operation-Pending flag. After the last pending overlapped command is completed(No-Operation-Pending flag set to true), an ASCII character “1” is placed into the OutputQueue, the Message Available (MAV) bit in the Status Byte sets, and the instrument goes backinto OQIS. Addressing the Model 7002 to talk will send the ASCII “1” to the computer.Note that the instrument always goes into OQAS when *OPC? is executed. If there are no pendingcommand operations (e.g. trigger model in idle state), the Model 7002 immediately placesan ASCII “1” in the Output Queue, sets the MAV bit and returns to OQIS.When used with the :INITiate or :INITiate:CONTinuous ON command, an ASCII “1” will notbe sent to the Output Queue and the MAV bit will not set until the Model 7002 goes back intothe idle state. The initiate operations are not considered finished until the instrument goes intothe idle state.When used with the *TRG command, an ASCII “1” will not be placed into the Output Queueand the MAV bit will not set until the operations associated with the *TRG command (and theinitiate command) are finished. The *TRG command is considered to be finished when the DeviceAction completes or when operation stops at a control source to wait for an event (see TriggerModel in paragraph 5.7).In order to use *OPC? exclusively with the *TRG command you will have to first force the completionof the initiate command so that only the *TRG command is pending. To do this, use the:INITiate:CONTinuous ON command to start the scan and then send the :ABORT command.The abort command places the instrument in the idle layer, which (by definition) completes theinitiate command. Since continuous initiation is on, operation will continue on into the TriggerModel. After sending the *TRG command, an ASCII “1” will be place in the Output Queue andthe MAV bit will set when the *TRG command is finished.5-52