Siemens SINUMERIK 840D sl Function Manual page 1461

If the user assigns a value of less than 100 to the Parameter "Status", then the associated
interface in data block DB 71 or DB 72 or DB 73, word 0 is deactivated (process completed).
The appropriate bit for the interface is set to 0 by FC 8.
The "Start" parameter does not need a signal edge for a subsequent job. This means that
new parameters can be assigned with "Start = TRUE" immediately when "Ready = TRUE" is
received.
Asynchronous transfer
To ensure that changes in the position of a tool are automatically signaled from PLC to tool
management (e.g., power failure during an active command or independent changes in the
position by the PLC), block FC 8 TM_TRANS with "TaskIdent": = 4 or 5 is called. This call
does not require interface activation by tool management.
If parameter "TaskIdent" = 5
the tool management reserves the location in addition to changing the position. The location
is only reserved if the tool has been transported from a real magazine to a buffer storage.
A relevant NC channel must be parameterized in the "TaskIdentNo" parameter.
The previous position of the tool is specified in parameters "OldToolMag", "OldToolLoc"
; the current position of the tool is specified
in parameters "NewToolMag", "NewToolLoc". Status = 1 must be specified.
With status 5, the specified tool remains at location "OldToolMag", "OldToolLoc". This
location must be a buffer (e.g., spindle). The real magazine and location must be specified in
the parameters "NewToolMag", "NewToolLoc"; the location is at the position of the buffer.
This procedure must always be used if the tool management is to be informed of the position
of a specific magazine location. This procedure is used for alignment in search strategies.
Note
It is not permissible to abort the transfer (e.g., by an external signal RESET). The "Start"
parameter must always retain the 1 signal until the "Ready" and/or "Error" parameters <> 0.
An error code <> 0 indicates incorrect parameterization.
Note
For further details on tool management (also with regard to PLC) refer to the Description of
Functions Tool Management. In addition, PI services for tool management via FB 4, FC 7
and FC 22 are available.
Basic logic functions: PLC basic program solution line (P3 sl)
Function Manual, 11/2006, 6FC5397-0BP10-2BA0
Detailed description
2.12 Block descriptions
187