Hello Leith,

To be honest - On a scale of 1 to 10 on "protocol knowledge" I have a 1 ;-).

I need to use several commands with different processing times. If I delay in general, the process will be longer than a manual process. Therefore I need to know when the instrument is ready to receive the next command.

This is a part of the interface definition (roughly translated):
The instrument is always "ready to receive" as it uses an interrupt control to process the interface data. After each CR received the device transmits XOFF. The command is being processed and after completion XON is send by the instrument.

As for your explanation. Would it be sufficient to "send" a command and then loop the "read" until Chr(17) is send by the instrument?

Thanks for your help
Robert