Keithley 2750 User Manual page 327

12-4 Common Commands
NOTE
C *OPC? — operation complete query
Description
When this common command is sent, an ASCII "1" will be placed in the Output Queue
after the last pending operation is completed. When the Model 2750 is then addressed to
talk, the "1" in the Output Queue will be sent to the computer.
The "1" in the Output Queue will set the MAV (Message Available) bit (B4) of the Status
Byte Register. If the corresponding bit (B4) in the Service Request Enable Register is set,
the RQS/MSS (Request for Service/Master Summary Status) bit in the Status Byte Regis-
ter will set.
When used with the Initiate Immediately command (:INITiate), a "1" will not be placed
into the Output Queue until the Model 2750 goes back into the idle state. The :INIT com-
mand operation is not considered finished until the Model 2750 goes back into the idle
state. See the description for *WAI for more information on command execution.
The execution of OPC? is not completed until it has placed the "1" in the Output Queue.
Programming example – The following command sequence demonstrates how to use
*OPC? to signal the end of a measurement process:
SYST:PRES
INIT:CONT OFF
ABORt
TRIG:COUN 1
SAMP:COUN 5
INIT
*OPC?
After all five measurements are performed and the instrument returns to the idle state, an
ASCII '1' will be placed in the Output Queue. After addressing the Model 2750 to talk,
the '1' from the Output Queue is sent to the computer.
SYST:PRES
The following commands take a long time to process and may benefit from
using *OPC or *OPC?:
• *RST and SYST:PRES
• *RCL and *SAV
• ROUT:MULT:CLOS and ROUT:MULT:OPEN – Only if the <clist> is long.
• CALC2:IMM and CALC2:IMM?– Only when performing the standard
deviation calculation on a large buffer. A 10,000 point buffer takes around
5.75 seconds.
' Returns 2750 to default setup.
' Disables continuous initiation.
' Aborts operation. Places 2750 in idle.
' These two commands configure the 2750
' to perform five measurements.
' Starts measurement process.
' Sends OPC? command.
' Returns 2750 to default setup.
Model 2750 Multimeter/Switch System User's Manual
Places a "1" in output queue after all
pending operations are completed