Siemens SINUMERIK 840Di Function Manual page 963

ASUBs
Asynchronous subprograms (ASUBs) can be used to activate any selected function in the
NC. Before an asynchronous subprogram can be started from the PLC, it must be ensured
that it is available and prepared by the NC program or by FB 4 PI services (ASUB). ASUBs
can only be started in MDA or Automatic mode with running parts program.
Once prepared in this way, it can be started at any time from the PLC. The NC program
running on the channel in question is interrupted by the asynchronous subprogram. The
asynchronous subprogram is started by FC 9.
Note
If an asynchronous subprogram has not been prepared by an NC program or by FB 4
(ASUB) (e.g., if no interrupt no. has been assigned), a start error is output.
Power Line Basic PLC Program (P3)
Function Manual, 08/2005 Edition, 6FC5397-0BP10-0BA0
2.7 Structure and functions of the basic program
Detailed description
2-51