Siemens MOBY FC 56 Technical Description page 87

In status 23 the following can occur.
S an old MDS enters the transmission window. Since the Next MDS bit is set, no
processing of the temporarily stored command occurs. Status 21 is valid.
S a new/next MDS enters the transmission window. This immediately becomes
the old/current MDS and the Next MDS bit is reset. The command is issued and
status 27 is valid. Once the command has been processed, status 3 is valid
again (another command can be issued for this MDS).
In status 3 the following can occur.
S another command can be issued by the FC 56. Status 27 is then valid.
S a NEXT command can be issued by the FC 56. Processing of the current/old
MDS is terminated. Status 9 is valid.
S the old/current MDS leaves the transmission window. Status 5 is then valid.
In status 5 the following can occur
S the old MDS returns to the transmission window. Status 3 is valid.
S a NEXT command is issued by the FC 56. The filehandler sets the Next MDS
bit internally and goes into status 11 (waiting for the next/new MDS).
S a command is issued by the FC 56. Since no MDS is present, this command
will be temporarily stored by the filehandler (not with MDS_IO_control 1). Status
17 is valid.
S a new MDS enters the SLG transmission window. Status 1 is valid.
Note
Continuous MDS control is effective in status 1 (MDS_IO_control 0 only).
The old/current MDS left the field in status 3 (status 5). The new MDS enters the
field, therefore status 1. The following can now occur:
S
a command can be issued by the FC 56. This is an error condition, since the
old/current MDS has not been terminated by a NEXT command and a
command for the new MDS has already been issued.
S
the new MDS leaves the SLG transmission window again. This is also an error
condition, since the new MDS has not been processed by a command (the new
MDS "slips through"). An error message is output when the filehandler issues
the next command.
FC 56
J31069-D0155-U001-A0-7618
Entry/Exit Check of an MDS in an SLG Field
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