Opc?  Operation Complete Query - Keithley 7001 Instruction Manual

IEEE-488 Reference
*OPC?  operation complete query
5.10.7
Purpose
Format
Description
5-48
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Place a "1" in the Output Queue after all overlapped commands are completed.
*OPC?
On power-up, or when *CLS or *RST is executed, the Model 7001 goes into the Operation
Compee Command Query Idle State (OQIS). In this state there are no pending overlapped com-
mands. There are three overlapped commands used by the Model 7001:
:INITiate
:INITiate:CONTinuous ON
*TRG
When the *OPC? command is sent, the Model 7001 exits from OQIS and enters the Operation
Complete Command Active State (OQAS). In OQAS, the instrument continuously monitors the
No-Operation-Pending flag. After the last pending overlapped command is completed (No-Op-
eration-Pending flag set to true), an ASCII character "1" is placed into the Output Queue, the
Message Available (MAV) bit in the Status Byte sets, and the instrument goes back into OQIS.
Addressing the Model 7001 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 pend-
ing command operations (e.g. trigger model in idle state), the Model 7001 immediately places
an 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 not
be sent to the Output Queue and the MAV bit will not set until the Model 7001 goes back into
the idle state. The initiate operations are not considered finished until the instrument goes into
the idle state.
When used with the *TRG command, an ASCII "1" will not be placed into the Output Queue
and the MAV bit will not set until the operations associated with the *TRG command (and the
initiate command) are finished. The *TRG command is considered to be finished when the De-
vice Action completes or when operation stops at a control source to wait for an event (see Trig-
ger Model in paragraph 5.7).
In order to use *OPC? exclusively with the *TRG command you will have to first force the com-
pletion of 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 the
initiate command. Since continuous initiation is on, operation will continue on into the Trigger
Model. After sending the *TRG command, an ASCII "1" will be place in the Output Queue and
the MAV bit will set when the *TRG command is finished.