BECKHOFF BK7000 - Manual (Page 22)

ControlNet coupler BK7000 in the ControlNet
21 BK 7000
Calculating rules for terminal bus input and output data
sizes
There are three options for mapping analog terminals and other complex
terminals: data only (if possible), complete without word-alignment, or
complete with word-alignment. The input and output data sizes depend on
which mapping option is chosen.
If no config data are sent when connecting the Assembly object, the
BK7000 will at first try to use the most recently used mapping option. Fai-
ling that, it will try the options in the following order, choosing the first opti-
on that will make the data sizes match with the sizes received from the
scanner. This option will then be stored in the register table.
Rule 1 Analog terminals are mapped with data only. Other complex terminals are
mapped with data only if applicable, otherwise they are mapped complete-
ly, without word-alignment.
Rule 2 All complex terminals are mapped completely, without word-alignment.
Rule 3 Analog terminals are mapped with data only, other complex terminals are
mapped with data only if applicable, otherwise they are mapped complete-
ly, with word-alignment.
Rule 4 All complex terminals are mapped completely, with word-alignment.
If config data are sent when connecting the Assembly object, the input and
output data sizes are calculated using the selected option.
If the 2-Byte-PLC-interface or the 2-Byte-Diag-interface are enabled by the
config data, 2 additional bytes of input and output data are needed for each
enabled interface.
The data of the Assembly object have the following stucture:
Offset (in bytes) Meaning Remark
0 Transport header
2 Scanner / Adapter status
6 2-Byte-PLC-interface Optional
8 2-Byte-Diag-Interface Optional
10 Complex terminals (left to right)
10 + size of complex terminals Digital terminals (left to right)
Note that the terminal data begin at offset 8 or 6 if any or both of the optio-
nal interfaces are disabled.