Siemens SINUMERIK 840D sl Function Manual page 1305

2.6 Interface structure
Interface data blocks
Mapping in interface data blocks is necessary due to the large number of signals exchanged
between the NCK and PLC. These are global data blocks from the viewpoint of the PLC
program. During system start-up, the basic program creates these data blocks from current
NCK machine data (no. of channels, axes, etc.). The advantage of this approach is that the
minimum amount of PLC RAM required for the current machine configuration is used.
2.6.1 PLC/NCK interface
General
The PLC/NCK interface comprises a data interface on one side and a function interface on
the other. The data interface contains status and control signals, auxiliary functions and G
functions, while the function interface is used to transfer jobs from the PLC to the NCK.
Data interface
The data interface is subdivided into the following groups:
• NCKspecific signals
• Mode-groupspecific signals
• Channelspecific signals
• Axis/spindle/drivespecific signals
Function interface
The function interface is formed by FBs and FCs. The figure below illustrates the general
structure of the interface between the PLC and the NCK.
Basic logic functions: PLC basic program solution line (P3 sl)
Function Manual, 11/2006, 6FC5397-0BP10-2BA0
Detailed description
2.6 Interface structure
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