Siemens SINUMERIK 840Di Function Manual page 480

Detailed Description
2.1 Predefined auxiliary functions
Bit1: Output duration one OB40 cycle (quick acknowledgment)
An auxiliary function with quick acknowledgment is output to the NC/PLC interface before the
next OB1 cycle. Auxiliary-function-specific change signals indicate to the PLC user program
that the auxiliary function is valid.
The auxiliary function is acknowledged immediately by the PLC basic program in the next
OB40 cycle. Acknowledgment of the auxiliary function is not confirmation that the
corresponding PLC user function has been executed. The auxiliary function is still executed
in the OB1 cycle. Next output of the auxiliary functions to the PLC is therefore not possible
until after this OB1 cycle has run completely. This is noticeable in continuous-path mode
(drop in path velocity) especially if auxiliary functions with quick acknowledgment are output
in several consecutive part program blocks.
With auxiliary functions with quick acknowledgment, it cannot be guaranteed that the PLC
user program will respond in synchronism with the block.
Note
Parameterization of the output behavior of auxiliary functions as "quick auxiliary functions" is
only possible in conjunction with user-defined auxiliary functions.
Bit2: No predefined auxiliary function
A predefined auxiliary function is treated like a user-defined auxiliary function if
"No predefined auxiliary function" is set. The auxiliary function then no longer triggers the
corresponding system function but is only output to the PLC.
Example:
Reconfiguration of auxiliary function "Position spindle" with index 9 (see table in Chapter:
Predefined auxiliary functions), to a "user-defined" auxiliary function with normal
acknowledgment and output of the traversing movement.
MD22080 $MC_AUXFU_PREDEF_SPEC [ 9 ] = 'H25' (100101
Bit3: No output
The auxiliary function is not output to the PLC.
Bit4: Spindle response following acknowledgment
The corresponding spindle function is only started after acknowledgment by the PLC.
Bit5: Output prior to motion
The auxiliary function is output before the traverse movements programmed in the part
program block (path and/or block-related positioning axis movements).
2-6
)
B
Auxiliary Function Output to PLC (H2)
Function Manual, 08/2005 Edition, 6FC5397-0BP10-0BA0