Siemens SIMATIC TIWAY 1 - Manual (Page 28)

OPERATION AND APPLICATION
UNILINK HOST ADAPTER 2–18
USER MANUAL
offline, and if the secondary is an HIU. The Network Manager normally cycles
through the secondary device log and checks to see if there are any outstanding
directives or responses. In addition, it will also select one secondary device
address per cycle to perform a link status check. The selected secondary address
initially begins with secondary number one and continues with the next
secondary address number until reaching the maximum secondary address
specified in the CONFIGURE ADAPTER command. Background monitoring
then starts over again with address one.
The current link status determines what action to take when monitoring a
device. If the current link status for the selected secondary address is offline,
the Network Manager will issue the initialization sequence. If there is no
response, the Network Manager will assume that the device is not in the
network and will not retry the message. If the device does respond, its status
will be updated and if it is an HIU, buffers will be allocated. This means that any
time that a valid secondary device is connected to the network, it will be brought
online.