Siemens SINUMERIK 840D sl Function Manual page 1181

2.12.15 FC 9: ASUB startup of asynchronous subprograms
Description of functions
The FC ASUB can be used to trigger any functions in the NC. Before an ASUB can be
started from the PLC, it must have been selected and parameterized by an NC program or
by FB 4 (PI service ASUB). The channel and interrupt number must tally with the parameters
in FC 9.
An ASUB prepared in this way can be started by the PLC at any point in time. The NC
program running on the channel in question is interrupted by the asynchronous subprogram.
Only one ASUB can be started in the same channel at a time. If the start parameter is set to
logical 1 for two FC 9s within one PLC cycle, the ASUBs are started in the sequence in
which they are called.
The start parameter must be set to logic 0 by the user once the ASUB has been terminated
(Done) or if an error has occurred.
For the purpose of job processing, every FC ASUB requires its own WORD parameter "Ref"
from the global user memory area. This parameter is for internal use only and must not be
changed by the user. The parameter Ref is initialized with the value 0 in the first OB 1 cycle
and, for this reason, every FC 9 must be called absolutely. Alternatively, the user can
initialize parameter "Ref" with a value of 0 during startup. This option makes conditional calls
possible. When a conditional call is activated by parameter "Start" = 1, it must remain active
until parameter "Done" has made the transition from 1 to 0.
Note
The FB 4 call must be terminated before the FC 9 can be started. FC 9 cannot be started if
"Emergency off" is set. Neither can FC 9 be started if the channel reset is active.
Basic logic functions: PLC Basic program powerline (P3 pl)
Function Manual, 11/2006, 6FC5397-0BP10-2BA0
Detailed description
2.12 Block descriptions
197