Siemens SINUMERIK 840D sl Function Manual page 730

Software Cams, Position Switching Signals (N3)
Output of cam signals
9.3.4 Timer-controlled cam signal output
Timer-controlled output
A significantly higher degree of accuracy can be achieved by outputting the cam signals
independently of the position control cycle using a timer interrupt.
The following general machine data can be set to select timer-controlled output to the 4 NCU
onboard outputs for 4 cam pairs:
MD10480 SW_CAM_TIMER_FASTOUT_MASK
(screen form for the output of cam signals via timer interrupts on NCU)
In this case, the minus and plus signals of a cam pair are gated for output as one signal.
Signal generation
The following machine data must be used beforehand to specify
how the signals are to be gated:
MD10485 SW_CAM_MODE Bit 1
Bit
Not set
set
Note
This function runs independently of the assignment in machine data:
MD10470 SW_CAM_ASSIGN_FASTOUT_1 or
MD10471 SW_CAM_ASSIGN_FASTOUT_2 or
MD10472 SW_CAM_ASSIGN_FASTOUT_3 or
MD10473 SW_CAM_ASSIGN_FASTOUT_4.
The onboard byte may not be used more than once at any one time.
Restrictions
The following applies to the mutual position of the cam positions:
Only one timer-controlled output takes place per interpolation cycle.
If signal changes for more than one cam pair are active in the same interpolation cycle, the
output is prioritized:
The cam pair with the lowest number (1...32) determines the output time for all active
signals, i.e. the signal change of the other cam pairs takes place at the same time.
730
Signal generation
Inversion of signal response of plus cam when:
plus cam - minus cam ≥ 180 degrees
No inversion of signal response of plus cam:
plus cam - minus cam ≥ 180 degrees
Function Manual, 03/2009, 6FC5397-1BP10-4BA0
Extended Functions