Siemens SINUMERIK 840D sl Function Manual page 39

Read setpoint
The current NCK value of the digital outputs can be read by the PLC user program:
DB10, DBB64 or DBB186 ... (setpoint for digital NCK outputs)
Please note that this setpoint ignores disabling and the PLC setting mask. Therefore, the
setpoint can differ from the actual signal state at the hardware output (see fig.).
RESET/end of program
At the end of the program or on RESET, a specific default value can be assigned by the PLC
user program to every digital output in accordance with requirements, using the overwrite
mask, setting mask or disable signal.
POWER ON
After POWER ON, the digital outputs are set to "0" in a defined manner. This can be
overwritten from the PLC user program according to the specific application using the masks
described above.
Digital NCK outputs without hardware
If digital NCK outputs, as defined in the following general machine data, are written by the
part program, but are not available as hardware, no alarm is output. The NCK value can be
read by the PLC (IS "setpoint ...").:
MD10360 $MN_FASTIO_DIG_NUM_OUTPUTS
Applications
This function allows digital hardware outputs to be set instantaneously by bypassing the PLC
cycles. Time-critical switching functions can thus be triggered in connection with the
machining process and under program control (e.g., on block change).
For example, digital NCK outputs are required for the following NC functions:
● Position-switching signals
References:
/FB2/ Function Manual, Extended Functions; Software Cam, Position-Switching Signals (N3)
● Output of comparator signals
The NCK outputs are assigned to the NC functions separately for each function via machine
data. Multiple assignments of outputs are checked during booting and indicated by an alarm.
Extended Functions
Function Manual, 09/2009, 6FC5397-1BP20-0BA0
A4: Digital and analog NCK I/Os
1.2 NCK I/O via PLC
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