Siemens SINUMERIK 840D sl Function Manual page 33

Weighting factor
The evaluation factors of the following general machine data allow each individual analog
NCK input and output to be adapted to the AD or DA converters of the analog I/O module
used:
MD10320 $MN_FASTIO_ANA_INPUT_WEIGHT[hw]
MD10330 $MN_FASTIO_ANA_OUTPUT_WEIGHT[hw]
If the correct weighting factor is set, the value set in system variable $A_OUTA[n] generates
the corresponding voltage value in millivolts at analog output [n].
Example for 840D
Analog-value range is 10 V (maximum modulation);
MD10330 $MN_FASTIO_ANA_OUTPUT_WEIGHT[hw] = 10000
(standard value for 840D)
$A_OUTA[1] = 9500 ; 9.5 V is output at analog NCK output 1
$A_OUTA[3] = -4120 ; -4.12 V is output at analog NCK output 3
Application for analog NCK inputs/outputs without hardware:
With a weighting factor of 32767, the digitized analog values for parts program and PLC
access are identical. In this way, it is possible to use the associated input or output word for
1:1 communication between the part program and the PLC.
Assignment to NC functions
Several NC functions are dependent on the functionality of the NCK I/Os.
Assignment of NCK inputs and outputs for these NC functions
is accomplished function-specifically via machine data, for instance:
MD21220 $MC_MULTFEED_ASSIGN_FASTIN (Multiple feedrates in one batch).
A byte address should be specified in the machine data for digital inputs/outputs. Each byte
is assigned separately.
Byte address
0
1
2
3
4
5
128
129
Extended Functions
Function Manual, 09/2009, 6FC5397-1BP20-0BA0
Assignment for the digital NCK inputs/outputs
None
1 to 4 (on-board I/O)
9
17
25
33
Inputs 1 to 8 of comparator byte 1
Inputs 9 to 16 of comparator byte 2
A4: Digital and analog NCK I/Os
and 5 to 8 (NCK output without hardware)
to 16 (external NCK I/Os)
to 24 (external NCK I/Os)
to 32 (external NCK I/Os)
to 40 (external NCK I/Os)
1.2 NCK I/O via PLC
33