Siemens SIMATIC TIWAY 1 User Manual page 29

OPERATION AND APPLICATION
If the background monitor detects a secondary that went offline and the auto
redundant media feature is active, the Network Manager will attempt to
contact the secondary on the alternate channel as described in the Redundant
Media section above.
You can obtain peak performance by consecutively numbering your secondary
devices and HIUs, starting with address 01, and by setting the largest
secondary device address value in the CONFIGURE ADAPTER command. This
will keep the Network Manager from spending time on device addresses that
will never exist on the network. Your applications software can request the link
status information with the REPORT SECONDARY LINK STATUS command,
code 32.
2–19 UNILINK HOST ADAPTER
USER MANUAL