5. Multicast > Port Reset
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Tsi574 User Manual
June 6, 2016
Integrated Device Technology
www.idt.com
5.4.4
Silent Discard of Packets
It is possible for the multicast engine to silently discard packets. The following are examples of
situations where a multicast packet is dropped:
•
A multicast group has no egress ports selected. The multicast mask and multicast vector for a
packet using this multicast group is empty.
•
If the multicast group has only one port selected which corresponds to the ingress port on which
the packet was received, the multicast vector is empty.
•
The multicast group contains a port with which the AUTODEAD bit is set in the
Multicast Maximum Latency Counter CSR” on page 384
In these cases, no interrupt is issued. No other information is latched regarding the packet(s) that were
dropped.
5.4.5
Port-writes and Multicast
Port-writes can be multicast to multiple output links, depending on the destinationID of the port-write.
Using the multicast feature improves the likelihood of delivery of port-writes for link failures.
5.5
Port Reset
When a port is powered down, the port looses configuration information that is stored for that
particular port. For example, multicast settings and port write settings return to their default power up
settings after a port reset. After port reset, there is no way to determine that the configuration for a
particular port is correct.
When one of the active ports is reset, the multicast mask is required to be re-bound to that port. Refer to
for more information
Only the copy of the packet is dropped.
If a blocked or failed port becomes unblocked, port-writes may be delivered late.
