Siemens SINUMERIK 840Di Function Manual page 513

Auxiliary function: M1 (conditional stop)
Overlaying parameterized output behavior
The parmeterized output behavior of auxiliary function: M1 is overlaid by the output behavior
defined in the following machine data:
MD20800 $MC_SPF_END_TO_VDI, Bit 1 (end of subroutine/stop to PLC)
Bit Value
1
Part program blocks without traverse movement
In a part program block without a traverse movement, all auxiliary functions are output in a
block immediately, irrespective of their parameterized output behavior.
Auxiliary Function Output to PLC (H2)
Function Manual, 08/2005 Edition, 6FC5397-0BP10-0BA0
Meaning
0 The auxiliary function M01 (conditional stop) is always output to the PLC. Quick
acknowledgment in not active because M01 is permanently assigned to auxiliary
function group 1 and is therefore always output at the end of the block.
1 Auxiliary function M01 (conditional stop) is always output to the PLC if function:
"Programmed stop" is activated via the HMI user interface.
In the case of quick acknowledgment, the M1 is output to the PLC during the movement.
While the function is not active, this does not interrupt continuous-path mode.
Supplementary conditions
3.2 Output behavior
3-3