Detailed description   
2.5 Linking PLC CPUs to 810D, 840D 
  Power Line Basic PLC Program (P3) 
2-24  Function Manual, 08/2005 Edition, 6FC5397-0BP10-0BA0 
2.5.1  Properties of PLC CPUs 
SINUMERIK 810D/840D/840Di PLC CPUs are based on standard SIMATIC CPUs in the S7-
300 family. As a result, they generally possess the same functions. Functional deviations are 
shown in the table above. Owing to differences in their memory system as compared to the 
S7 CPU, certain functions are not available (e.g., blocks on memory card, project on memory 
card).  
 
 
Note 
With the current SIMATIC CPUs, the PLC is not automatically started after voltage failure 
and recovery when a PLC Stop is initiated via software operation. In this instance, the PLC 
remains in the Stop state with an appropriate diagnostic entry for safety reasons. You can 
start the PLC only via software operation "Execute a restart" or by setting the switch to 
"Stop" and then "RUN". This behavior is also integrated in the current versions of the 
SINUMERIK PLC. 
 
2.5.2  Interface on 810D and 840D with integrated PLC 
Physical interfaces 
As the 810D and 840D systems have an integrated PLC, signals can be exchanged between 
the NCK and PLC directly via a dualport RAM. 
Exchange with operator panel and MCP 
Data are generally exchanged with the operator panel (OP), machine control panel (MCP) 
and handheld unit (HHU) on the 840D via the operator panel interface (OPI), the COM 
module being responsible for data transport. 
All devices specified above can also be operated on the multipoint interface (MPI) in the 
case of the 840 D. With the 810D, data communication with the operator panel (OP), 
machine control panel (MCP) and handheld unit (HHU) takes place only via the MPI. 
The programming device is connected directly to the PLC via the MPI (multipoint interface).