HP 8920B - Page 236

236
Common Command Descriptions
Using the *OPC? query by reading Output Queue
Bit 4 in the Service Request Enable Register is set to a value of zero (disabled).
The *OPC? query is sent to the Test Set at the end of a command message data
stream. The application program then attempts to read the *OPC? query response
from the Test Set’s Output Queue. The Test Set will not put a response to the
*OPC? query into the Output Queue until the commands have all finished.
Reading the response to the *OPC? query has the penalty that both the HP-IB bus and the
Active Controller handshake are in temporary holdoff state while the Active Controller
waits to read the *OPC? query response from the Test Set.
Example BASIC program
10 INTEGER Output_que_val
20 OUTPUT 714;"*SRE 0"! Disable Service Requests
30 OUTPUT 714;"DISP RFG;RFG:OUTP ’Dupl’;AMPL 0 dBm;FREQ 320
MHz;*OPC?"
40 ENTER 714;Output_que_val
50 !Program will wait here until all operations complete
60 PRINT "All operations complete."
70 END
Using the *OPC? query using the MAV bit in the Status Byte
Bit 4 in the Service Request Enable Register is set to a value of 1 (enabled). The
*OPC? query is sent to the Test Set at the end of a command message data stream.
The Test Set will request service when the MAV bit in the Status Byte register is
set to the TRUE, logic 1, state. After the service request is detected the application
program can take appropriate action. Refer to the
"HP-IB Service Requests" on
page 311
for further information.