Siemens SINUMERIK 840D sl Function Manual page 731

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
9.3.5 Independent, timer-controlled output of cam signals
Independent, timer-controlled cam output
Each switching edge is output separately per interrupt due to the timer-controlled,
independent (of interpolation cycle) cam output.
Interaction between cam signals due to:
● single output per interpolation cycle
● output time determined by highest priority cam pair (lowest cam pair number)
does not take place.
A total of eight timer-controlled cam outputs per interpolation cycle can be configured for
setting/resetting the four onboard outputs. The signal states of the plus and minus cams are
also made available as standard on the PLC interface for the timer-controlled variant, but
they are not relevant or accurate with a timer-controlled output.
Extended Functions
Function Manual, 03/2009, 6FC5397-1BP10-4BA0
Software Cams, Position Switching Signals (N3)
Output of cam signals
731