What was said above makes clear that overlapping execution is possible in principle for all commands. Equally, setting commands within one command line are not absolutely serviced in the order in which they have been received.
In order to make sure that commands are actually carried out in a certain order, each command must be sent in a separate command line, that is to say, with a separate IBWRT()-call.
In order to prevent an overlapping execution of commands, one of commands *OPC, *OPC? or *WAI must be used. All three commands cause a certain action only to be carried out after the hardware has been set and has settled. By suitable programming, the controller can be forced to wait for the respective action to occur.
Synchronization with *OPC, *OPC? and *WAI
| Command | Action after the hardware has settled | Programming the controller |
| *OPC | Setting the operation-complete bit in the ESR | - Setting bit 0 in the ESE - Setting bit 5 in the SRE - Waiting for service request (SRQ) |
| *OPC? | Writing a "1" into the output buffer | Addressing the instrument as a talker |
| *WAI | Executing the next command | Sending the next command |
Note:
The GPIB bus handshake is not stopped