Siemens Sinumerik 840D sl Programming Manual page 114

Additional functions
4.3 Eight-digit program number
Interrupt M96
Does not function in SINUMERIK 802D sl.
$MC_EXTERN_FUNCTION_MASK, Bit6 = 0
M96 Pxxxx
Addition of program number always to 4 digits with 0
$MC_EXTERN_FUNCTION_MASK, Bit6 = 1
M96 Pxxxx
There is no extension with 0, even if the program number has less than 4 digits. A program
number with more than 8 digits leads to an alarm.
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Programming Manual, 06/09, 6FC5398-7BP10-1BA0
ISO Milling