Glossary 
 
Basic logic functions: Appendix 
Function Manual, 11/2006, 6FC5397-0BP10-2BA0 
27 
MDA 
Control operating mode: Manual Data Automatic. In the MDA mode, individual program 
blocks or block sequences with no reference to a main program or subprogram can be input 
and executed immediately afterwards through actuation of the NC start key. 
Messages 
All messages programmed in the part program and → alarms detected by the system are 
displayed on the operator panel in plain text with date and time and the corresponding 
symbol for the cancel criterion. Alarms and messages are displayed separately. 
Metric measuring system 
Standardized system of units: For length, e.g., mm (millimeters), m (meters). 
Mirroring 
Mirroring reverses the signs of the coordinate values of a contour, with respect to an axis. It 
is possible to mirror with respect to more than one axis at a time. 
Mode group 
Axes and spindles that are technologically related can be combined into one mode group. 
Axes/spindles of a BAG can be controlled by one or more → channels. The same → mode 
type is always assigned to the channels of the mode group. 
Mode of operation 
An operating concept on a SINUMERIK control. The following modes are defined: → Jog, 
→ MDA, → Automatic. 
NC 
Numerical Control: Numerical control (NC) includes all components of machine tool control: 
→ NCK, → PLC, HMI, → COM. 
 
 
Note 
A more correct term for SINUMERIK 840D controls would be: Computerized Numerical 
Control 
 
NCK 
Numerical Control Kernel: Component of NC that executes the → part programs and 
basically coordinates the motion operations for the machine tool.