fido2100 3-Port Industrial Ethernet DLR Switch with IEEE1588
Data Sheet
April 10, 2013
2.3 Device Level Ring (DLR) Protocol Support
The fido2100 provides hardware support for a single-fault tolerant ring protocol. The DLR protocol
support for non-supervisor mode and support for supervisor mode can be enabled by setting appropriate
bits in the redundancy control register.
In non-supervisor mode, received non-erroneous DLR beacon frames from the active ring supervisor
through either port will be automatically dropped after extracting state information and restarting the
DLR beacon timers. Received non-erroneous DLR beacon frames may optionally be configured to be
delivered to the host CPU by setting appropriate bits in the redundancy control register. Irrespective of
this bit setting, beacon messages received from a different supervisor than active supervisor are always
forwarded to host CPU. The fido2100 can be configured to interrupt host CPU when ring beacon
frames from active supervisor are received through either port or are not received through either port
within ring beacon timeout period. The fido2100 can also be configured to interrupt host CPU when a
change of state is observed in ring beacon frames from active ring supervisor received through either
port. Neighbor check and multicast sign on frames received from either external port will be forwarded
only to host CPU and those from host CPU will be forwarded only through port number matching
source port number field in frame. Source identifier and sequence identifier fields of received neighbor
check frames are captured to identify received port later. Unicast sign on frames are treated as any
other unicast frame.
In supervisor mode, either one of the external ports can be placed in blocked mode by setting
appropriate port transmit/receive blocked bits in redundancy control register. All frame reception and
transmission will be blocked by the port in blocked mode with the exception of some special frames.
These special frames are described under port transmit/receive blocked bits in redundancy control
register. In supervisor mode, ring beacon frames can be automatically generated and transmitted
through unblocked ports to reduce the CPU load and their arrival through both ports are monitored. The
fido2100 can be configured to interrupt the host CPU when DLR beacon frames are received through
either port or are not received through either port within DLR beacon timeout period. The fido2100 can
also be configured to interrupt the host CPU when a change of state is observed in DLR beacon frames
are received from the active ring supervisor through either port. Received non-erroneous DLR beacon
frames may optionally be configured to be delivered to host CPU by setting appropriate bits in
redundancy control register. Irrespective of this bit setting, beacon messages received from a different
supervisor than self is always forwarded to host CPU.
In supervisor mode, neighbor check and multicast sign on frames received from either external port
will be forwarded only to the host CPU, and those from the host CPU will be forwarded only through
the port number matching the source port number field in the frame. The source identifier and sequence
identifier fields of received neighbor check frames and sign on frames are captured to identify the
received port later. Link/neighbor status frames received from either external port will be forwarded
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