Siemens 7SR51 Device Manual page 448

Instruments and Meters
8.2 Instruments
448
Roles of the ports
The following roles are defined for the
ports:
•
Root port role (R): A root port is
connected with the root switch, i.e. it
has a logical connection with it. With
internal switches, 1 of the 2 ports
always has the role of a root port.
•
Designated port role (D): A desig-
nated port can also establish a
connection with the root switch, but
in a different way. 1 of the 2 ports of
the internal switch normally has the
designated port role.
•
Alternate port role (A): An alternate
port can establish a connection in
case of a failure. In stable operation,
there must be exactly 1 alternate port
in 1 device per ring. In the absence of
a port with this role in a ring, the
redundancy is not ensured. The ring
is open.
– According to IEEE 802.3 the
receive output window is -14
dBm to -31 dBm.
– According to IEEE 802 the
output window of the trans-
mitter is between -14 dBm and
-20 dBm.
Port states
In addition to the role played by them,
ports have states assigned to them. The
following states are defined:
•
Forwarding state (F): This is in normal
operation the state of the ports which
play the root or designated role, i.e.
payload telegrams are always trans-
mitted.
•
Discarding state (D): Discarding state
means that telegrams are discarded
and not forwarded. In normal opera-
tion, only the port with the alternate
role has this status.
•
Learning state (L): This state is not
available in the internal switches. The
switch structure is such that the port
does not require a learning phase.
Normal status
In our example, port 1 shows the role
alternate and the status designated,
which means that this port does neither
accept nor transmit telegrams from and to
the device.
Reyrolle 7SR5, Overcurrent Protection Device, Device Manual
C53000-G7040-C014-1, Edition 11.2019