Siemens SIMATIC Ident Function Manual page 100

Programming communications modules
B.1 Programming the communication modules on PROFIBUS/PROFINET
Communication between communications module and PROFIBUS/PROFINET master
It must be possible to transfer both the cyclic (DP) and the acyclic data DP-V1 via
PROFIBUS DP.
①
②
The master may only send new commands to the slave (communications module) when the
CM is ready. Status information is used in cyclic communication to indicate that the
communications module is ready. The same applies to acknowledgments. The
communications module may only fetch new acknowledgments when a new
acknowledgment is actually waiting (i.e. has not yet been read). This information is also
indicated by status information.
Two condition codes are defined in the status information. Based on these, the
PROFIBUS/PROFINET master can recognize whether an acylic frame can be sent to or
from the communications module.
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Cyclic communication via PROFIBUS/PROFINET. Status information is exchanged (see section
"Cyclic control word between master and communications module (Page 102)" and "Methods of
operation with the communications module (Page 105)").
Acyclic communication via PROFIBUS/PROFINET. Commands and acknowledgements are
exchanged (see section "Command and acknowledgement telegrams (Page 109)").
FB 45 for MOBY U, MOBY D, RF200, RF300
Function Manual, 07/2012, J31069-D0166-U001-A4-7618