Siemens SINUMERIK 840Di Function Manual page 943

Compile-cycle signals
In addition to the standard signals exchanged between the PLC and NCK, an interface DB
for compile cycles is also generated if required (DB 9). The signals, which are dependent on
the compile cycles, are transmitted cyclically at the start of OB1.
Signals PLC/NC
The group of signals from the PLC to NC includes:
• Signals for modifying the highspeed digital I/O signals of the NC
• Keyswitch and emergency stop signals
Signals NC/PLC
The group of signals from the NC to PLC includes:
• Actual values of the digital and analog I/O signals of the NC
• Ready and status signals of the NC
Also output in this group are the handwheel selection signals from the MMC and the status
signals of the MMC.
The signals for handwheel selection are decoded by the basic program and entered in the
machine/axisspecific interface.
Power Line Basic PLC Program (P3)
Function Manual, 08/2005 Edition, 6FC5397-0BP10-0BA0
Detailed description
2.6 Interface structure
2-31