Siemens SINUMERIK 840D sl Function Manual page 46

A4: Digital and analog NC I/O for SINUMERIK 840D sl
2.2 Indirect I/O access via PLC
Overwrite mask
Every NC analog value set by the part program can be overwritten from the PLC using the
overwrite mask. The previous "NC value" is lost.
The following sequence has to be carried out to overwrite the NC value from the PLC:
1. The relevant PLC interface output <n> has to be set to the required analog value.
DB10 DBW170 ... (setpoint from the PLC for analog output <n> of the NC)
2. The "setpoint from the PLC" becomes the new "NC value" when the overwrite mask for the
relevant analog output is activated (edge change 0 → 1).
DB10 DBB166 (overwrite mask of analog NC outputs)
This value remains operative until a new value is programmed (from the PLC or from the part
program).
Setting mask
A PLC setting for each output can determine whether the current "NC value" (e.g. as specified
by the NC part program) or the "PLC value" specified via the setting mask should be output at
the hardware analog output.
The following sequence has to be carried out to define the "PLC value":
1. The relevant PLC interface output has to be set to the required analog value.
DB10 DBW170 ... (setpoint from the PLC for analog output <n> of the NC)
2. The setting mask must be set to "1" for the relevant analog output:
DB10 DBB167 (setting mask of the analog NC outputs)
Unlike the overwrite mask, the NC 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 NC value becomes active
again.
Note
The same setpoint is used at the PLC interface for the overwrite and setting masks.
Disable output
Analog NC outputs can be disabled individually from the PLC user program:
DB10 DBB168 (disable of the analog NC outputs)
In this case, the "0" signal is output at the hardware output.
In this case, 0 volt is output at the analog output.
Read setpoint
The current "NC value" of the analog outputs can be read from the PLC user program:
DB10 DBW210 ... (setpoint of analog output <n> of the NC)
Please note that this setpoint ignores disabling and the PLC setting mask. Therefore, the
setpoint can differ from the actual analog value at the hardware output.
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Function Manual, 10/2015, 6FC5397-1BP40-5BA3
Extended Functions