Cyclic Control Word Between Master And Communications Module - Siemens SIMATIC Ident Function Manual

Programming communications modules
B.2 Cyclic control word between master and communications module
The user must evaluate the acknowledgement state with higher priority. In other words,
when the user wants to send a frame to the ASM but a frame from the CM is waiting to be
fetched at the same time, the frame from the CM must be fetched first.
Both the command and the acknowledgment state are coded in 2 bits each. The two
statuses are stored in one byte.
B.2

Cyclic control word between master and communications module

The cyclic control word is used to synchronize frame traffic between master (FB/FC) and
slave (communications module). The actual acyclic command and acknowledgment frame
may not be started until this is indicated by the cyclic byte of the communications module in
the command or acknowledgment counter.
Cyclic word to communications module: I/O output
Figure B-2
102
Structure of the cyclic control word: Peripheral output
FB 45 for MOBY U, MOBY D, RF200, RF300
Function Manual, 07/2012, J31069-D0166-U001-A4-7618