Special memory (SM) and system symbol names
D.16 SMB86-SMB94 and SMB186-SMB194: Receive message control
S7-200 SMART
682 System Manual, 09/2015, A5E03822230-AC
The bits of the message control byte are used to define the criteria by which the message is
identified. The start of message and end of message criteria are defined. To determine the
start of a message, either of two sets of logically ANDed start of message criteria must be
true and must occur in sequence (in sequence means idle line followed by start character or
break followed by start character). To determine the end of a message, the enabled end of
message criteria is logically ORed. The equations for start and stop criteria are given below:
Start of Message = (il AND sc) OR (bk AND sc)
End of Message = ec OR tmr OR maximum character count reached
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