Siemens SINUMERIK 840D sl Function Manual page 45

Special case
If values for NCK analog outputs defined in machine data
MD10310 $MN_FASTIO_ANA_NUM_OUTPUTS
are programmed in the part program, but are not available as hardware, no alarm is output.
The NCK value can be read by the PLC (IS "setpoint ...").
Application
This function allows analog values to be output instantaneously by bypassing the PLC
cycles.
The analog NCK outputs are used in particular for grinding and laser machines.
Figure 1-4
Extended Functions
Function Manual, 01/2008, 6FC5397-1BP10-3BA0
Signal flow for analog NCK outputs
Digital and analog NCK I/Os (A4)
1.2 NCK I/O via PLC
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