Siemens SINUMERIK 840D sl Function Manual page 700

Software cams, position switching signals (N3)
9.3 Output of cam signals
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.
PLC interface
The NCK image of the onboard outputs and the status of the plus and minus cams is
displayed on the PLC interface.
These signals are irrelevant, however, or correspondingly inaccurate with the timer-
controlled cam output variant, as described in the following paragraphs. The signals for the
plus and minus cams are generated (once) in synchronism with the interpolation cycle and
transmitted together to the PLC.
Pulses shorter than an interpolation cycle are thus imperceptible on the PLC.
The onboard outputs are set and reset asynchronously to the interpolation cycle for each
interrupt. The status of the onboard outputs is detected and transmitted to the PLC in
synchronism with the update time of the PLC interface.
Depending on the current status at the moment the PLC interface is updated, pulses shorter
than one interpolation cycle are not visible or are displayed stretched by one or several IPO
cycles.
Further settings
If the response described here is to be applied,
bit 0=0 must be set in the following machine data:
MD10485 SW_CAM_MODE
700
Function Manual, 01/2008, 6FC5397-1BP10-3BA0
Extended Functions