IDT 89HPES64H16G2 User Manual page 191

IDT Multicast
Notes
PES64H16G2 User Manual
A side-effect of modifying the address due to multicast overlay processing is that the ECRC associated
with the original TLP may not be correct for the new modified TLP. Therefore, functions perform the
following ECRC processing:
– If multicast overlay processing is disabled, then no ECRC processing is performed as part of multi-
cast egress processing. The function continues to check and report ECRC errors for received
TLPs and this behavior is unaffected in any way by multicast.
– If a multicast TLP does not contain an ECRC, then no ECRC processing is performed as part of
multicast egress processing. If a multicast TLP contains an ECRC and multicast overlay
processing is enabled, then the following actions are performed.
– The ECRC of the original multicast TLP is checked while simultaneously the ECRC for the new
modified TLP is computed or "regenerated." This is implemented in the same pipeline stage such
that there is virtually no possibility of silent data corruption (e.g., a TLP bit flip that does not result
in a computed ECRC error in the original or regenerated ECRC).
– If no error is detected in the ECRC associated with the original TLP, then the modified TLP is
forwarded with the regenerated ECRC. If an error is detected in the ECRC associated with the
original TLP, then the modified TLP is forwarded with inverted regenerated ECRC (i.e., the
computed ECRC of the modified TLP is inverted). No errors are reported due to multicast egress
processing.
14 - 5 April 5, 2013