Agilent Technologies 8712ET Programmer's Manual page 38

NOTE
The following is a procedure for passing control:
1. Send the controller's GPIB address to the analyzer with the *PCB
command.
2. Clear the analyzer's status registers with the *CLS command.
3. Enable the analyzer's status registers to generate a service request
when the Operation Complete bit is set. (Send *ESE with a value of 1
and *SRE with a value of 32.)
4. Enable the controller to respond to the service request.
5. Send the command that requires control of the bus followed by the
*OPC command.
6. Pass control to the analyzer and wait for the service request. The
service request indicates that the command has been completed and
control has been passed back to the controller.
For this procedure to work properly, only the command that requires
control of the bus should be pending. Other overlapped commands should
not. For more information on overlapped commands, see
"Synchronizing the Analyzer and a Controller."
Programmer's Guide
Passing Control
Passing Control
Chapter 2,
3-3