Siemens SINUMERIK 840D sl Function Manual page 1015

2.5 Linking PLC CPUs to 810D, 840D
2.5.1 General
The AS 300 family is used as the PLC for all systems. The essential difference between the
NCU variants lies in the method by which they are linked. On the 840D and 810D, the PLC
314 CPU (user memory capacity up to 128 KB) or PLC 315-2 DP (user memory capacity up
to 288 KB) is integrated as a submodule into the NC unit.
The PLC/CPU 315-2 DP also supports distributed I/Os on the PROFIBUS (L2DP). The
relevant performance data for individual PLC CPUs can be found in the above table or in
Catalog FT70.
2.5.2 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.
Basic logic functions: PLC Basic program powerline (P3 pl)
Function Manual, 11/2006, 6FC5397-0BP10-2BA0
Detailed description
2.5 Linking PLC CPUs to 810D, 840D
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