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EZ-NET Network, COM-LINK Serial
MN05013005E
354
Operating principle of the COM-LINK connection
The active station at the COM-LINK must be in RUN mode.
Data can only be exchanged with the active station in RUN
mode.
The remote station must be in RUN or STOP mode.
The active station scans the remote station. The entire READ
marker range is transferred as a string. The entire WRITE
marker range is transferred as a string.
Sign of life detection COM-LINK, diagnostics contact ID09
In order to determine the proper functioning of the COM-LINK
connection, the diagnostics contact ID09 is provided on the
active station of the COM-LINK connection.
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Data consistency
The data is located in the image range (data range storing
the marker states) of the active station (1MD..) as well as in
the image range of the remote station (MD..)
Each station writes data to its own image range
asynchronously for data communication. As the serial
interface transfers large data volumes slower than the
devices overwrite the image ranges, the following applies:
one marker double word 1MD.., MD.. is consistent.
Within a program cycle, a marker double word that is
overwritten via COM-LINK is not constant. The data via the
COM-LINK is written to the status image over the course of
the program cycle. This means that a different marker value
can be present at the start of the program cycle to after the
write operation via COM-LINK.
