Siemens SINUMERIK 840Di Function Manual page 941

2.6 Interface structure
2.6
Interface data blocks
The PLC user interfaces on the 840D and 810D are identical except for the data volume.
Mapping in interface data blocks is required on account of the large number of signals.
These are global data blocks from the viewpoint of the PLC program. During system startup,
the basic program creates these data blocks from current NC 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.
Power Line Basic PLC Program (P3)
Function Manual, 08/2005 Edition, 6FC5397-0BP10-0BA0
Detailed description
2.6 Interface structure
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