Siemens SINUMERIK 840D Function Manual page 414

N3: Software cams, position switching signals
13.3 Output of cam signals
In this case, the minus and plus signals of a cam pair are logically combined for output as one
signal.
Signal generation
Previously, it had to be specified in which way the signals to be logically combined should be
generated. This is realized using bit 1 in machine data:
MD10485 SW_CAM_MODE (behavior of the software cams)
Bit
1
Note
This function operates independently of the HW assignment selected in MD10470 ... MD10473.
The onboard byte may not be used a multiple number of times.
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 NC image of the onboard outputs and the status of the plus and minus cams is displayed
at the PLC interface.
However, these signals are irrelevant or correspondingly inaccurate for the timer-controlled
cam output version, as described in the following paragraphs. The signals for the plus and
minus cams are generated (once) in synchronism with the interpolator clock cycle and
transmitted together to the PLC.
Pulses shorter than an interpolator clock cycle are therefore not visible in the PLC.
The onboard outputs are set and reset asynchronously to the interpolator clock 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 interpolator clock cycle are not visible or are displayed stretched by one or several IPO
cycles.
414
Value Signal generation
0 Inversion of the signal behavior of the plus cam when:
plus cam - minus cam ≥ 180 degrees
1 No inversion of the signal behavior of the plus cam when:
plus cam - minus cam ≥ 180 degrees
Axes and spindles
Function Manual, 06/2019, A5E47437747B AA