Siemens SINUMERIK 840D sl Function Manual page 46

A4: Digital and analog NCK I/Os
1.2 NCK I/O via PLC
Function
The value of the analog output [n] can be defined directly in the part program using system
variable $A_OUTA[n].
Before output to the hardware I/Os, the analog value set by the NCK can be changed by the
PLC (see fig.).
Disable output
The PLC user program is capable of disabling the NCK outputs individually using interface
signal
DB10 DBB168 (disable analog NCK outputs).
In this case, 0 volts is output at the analog output (see fig.).
Overwrite mask
Every NCK analog value set by the NC part program can be overwritten from the PLC using
the overwrite mask. The previous NCK value is then lost (see fig.).
The following routine has to be carried out to overwrite the NCK value from the PLC:
1. The output n in question must be preset with the required analog value at PLC interface
2. The PLC setting value becomes the new NCK value when the overwrite mask for the
This value remains valid until a new analog value is set for the NCK by the part program, for
example.
Setting mask
Furthermore, a PLC setting for each output can determine whether the current NCK value
(e.g., as specified by the NC part program) or the PLC value specified via the setting mask
(DB10, DBB167) should be sent to the hardware analog output (see fig.).
The following routine has to be carried out to define the PLC value:
1. The output n in question must be preset with the required analog value at PLC interface
2. The setting mask (DB10, DBB167) must be set to "1" for the analog output in question.
Unlike the overwrite mask, the current NCK value is not lost when a value is set in the setting
mask. As soon as the PLC sets "0" in the corresponding setting mask, the NCK value
becomes active again.
Note
The same setting value (DB10, DBB170 - 185) is used at the PLC interface for the overwrite
and setting masks.
46
DB10 DBB170 - 185 (PLC setting value for NCK analog output n).
relevant analog output (DB10, DBB166) is activated (signal transition 0 → 1).
DB10 DBB170 - 185 (PLC setting value for NCK analog output n).
Function Manual, 09/2009, 6FC5397-1BP20-0BA0
Extended Functions