Descriptions of the PLC subroutines   
3.2 Conventions for the symbols used in the subroutines 
  PLC Subroutines Manual 
32  Operating Instructions, 12/2012, 6FC5397-2EP10-0BA0 
3.2  Conventions for the symbols used in the subroutines 
The symbols used in the subroutines follow the conventions listed below:  
●  Leading characters designate the destinations of interface signals 
–  P_: to PLC interface 
–  H_: to HMI interface 
–  N_: to NCK interface 
–  M_: to MCP interface 
●  Subsequent characters are for areas 
–  N_: NCK 
–  C_: Channel 
–  1_: Axes 
–  M_: MCP 
Other short forms of the symbols 
–  HWL: Hardware Limit 
–  HW: Handwheel 
–  RT: Rapid Traverse 
–  TK: Traverse key 
–  ACT: Active 
–  SEL: Selected 
●  A symbol consists of a maximum of 11 upper case characters and numbers (including the 
leading character). Except for underlines, you cannot use any other special symbols like 
=, +, -, [ ], etc. 
Symbol tables 1 to 2 
The symbol tables 1 to 2 are for the manufacturer-defined SINUMERIK 808D I/O. Here you 
can define input/output tables for your machines. 
Symbol tables 3 to 5, 7 to 13 
These ten symbol tables are reserved for the subroutines. 
 
 
Note 
Important! 
If the colour of a symbol is displayed in red, this indicates that the naming does not follow the 
rules of the PLC Programming Tool. In this case, you must check: 
  whether the name uses special symbols like =, +, -, [ ], etc.. 
  whether the leading character is a number. 
If there is a red wave under a symbol name or address, it indicates that you have used the 
same symbol name or address for another symbol (there is also a red wave under its name 
or address). In this case, you must check the repeated name or address and change it.