Siemens SINUMERIK 840Di Function Manual page 936

Detailed description
2.5 Linking PLC CPUs to 810D, 840D
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).
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Power Line Basic PLC Program (P3)
Function Manual, 08/2005 Edition, 6FC5397-0BP10-0BA0