Siemens SINUMERIK 840D sl Function Manual page 44

A4: Digital and analog NCK I/Os
1.2 NCK I/O via PLC
Weighting factor
The weighting factor in general machine data can be used to adapt the analog NCK inputs to
different analog-to-digital converter hardware variants for the purpose of reading in the part
program (see figure):
MD10320 $MN_FASTIO_ANA_INPUT_WEIGHT[hw]
In this machine data, it is necessary to enter the value x that is to be read in the part program
with the system variable $A_INA[n], if the corresponding analog input [n] is set to the
maximum value or if the value 32767 is set for this input via the PLC interface. The voltage
level at the analog input is then read with system variable $A_INA[n] as a numerical value
with the unit millivolts.
Binary analog-value display
See "Analog-value representation of the NCK analog input/output values".
Analog NCK input without hardware
The following values are read in the case of parts-program access to analog NCK inputs that
are defined via machine data, but are not available as hardware inputs:
MD10300 $MN_FASTIO_ANA_NUM_INPUTS
● The setpoint set by the PLC,
● Otherwise 0 volts
This makes it possible to use the functionality of the analog NCK inputs from the PLC user
program without I/O hardware.
Applications
The analog NCK inputs are used particularly for grinding and laser machines (e.g., for the
"analog calipers" NC function).
Fast analog NCK inputs
The fast analog inputs must be isochronous.
The assignment is defined by the machine data:
MD10384 $MN_HW_CLOCKED_MODULE_MASK
44
if the IS "PLC setting value for analog NCK inputs"
is set to "1" (see fig.).
Function Manual, 09/2009, 6FC5397-1BP20-0BA0
Extended Functions