Siemens SINUMERIK 840D sl Function Manual page 838

P3: Basic PLC program for SINUMERIK 840D sl
13.9 Interface structure
Compile-cycle signals
In addition to the standard signals exchanged between the PLC and NCK, an interface data
block for compile cycles is also generated if required (DB9). The associated signals, which are
dependent on the compile cycles, are transmitted cyclically at the start of OB1. The basic
program starts transmission at the lowest address and works up to the highest. First, signals
are transferred from the PLC to the NCK, then from the NCK to the PLC. The user must
synchronize the NCK and PLC as necessary (e.g. using the semaphore technique). Signal
transmission is asynchronous between NCK and PLC. This means, for example, that active
NCK data transmission can be interrupted by the PLC. This can mean that data is not always
consistent.
PLC/NCK signals
The group of signals from the PLC to NCK includes:
● Signals for modifying the digital and analog I/O signals of the NCK
● Keyswitch and emergency stop signals
Figure 13-3
838
PLC/NCK interface
Function Manual, 01/2015, 6FC5397-0BP40-5BA2
Basic Functions