
IDT Multicast
PES32NT24xG2 User Manual
17 - 11
January 30, 2013
Notes
When the OVRSIZE field value is six or greater, NT multicast address overlay processing is performed
on all NT multicast TLPs transmitted by the port as described below.
–
Address bits in the NT multicast TLP with bit positions greater than or equal to OVRSIZE are
replaced by the corresponding address bits in the multicast overlay base address. The multicast
overlay base address is contained in the Multicast Overlay BAR Low (MCBARL) field in the
NTMCOVRxBARL register and the Multicast Overlay BAR High (MCBARH) field in the MCOVR-
BARH register.
–
Address bits less than OVRSIZE are not modified. As a result of multicast overlay processing, a
multicast TLP with an original address above 4 GB may be translated into a multicast TLP with
address below 4 GB, and vice-versa. Thus, address translation may change the size of a multicast
TLP header (e.g., from 4 DWords to 3 DWords).
–
Unlike transparent multicast, for NT multicast the OVRSIZE field in the NTMCOVRxBARL register
must not be set to less than six. Otherwise the operation of NT multicast egress processing is
undefined. As noted earlier, NT multicast address overlay can be explicitly disabled via the
NTMCAOE bit in the NT Multicast Control (NTMCC) register.
A side-effect of modifying the TLP’s address and requester ID due to NT multicast overlay processing is
that the ECRC associated with the original TLP may not be correct for the new modified TLP. Therefore,
egress ports perform the following ECRC processing.
1
–
If NT multicast overlay processing is disabled, then no ECRC processing is performed as part of
NT multicast egress processing.
–
If an NT multicast TLP does not contain an ECRC, then no ECRC processing is performed as part
of NT multicast egress processing.
–
If an NT multicast TLP contains an ECRC and NT multicast overlay processing is enabled (i.e.,
either requester ID overlay or address overlay), 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).
After performing egress processing of an NT multicast TLP, the port transmits the TLP on the link. No
routing checks are performed and no errors are reported due to NT multicast egress processing.
–
The NT multicast TLP transmitted by a port must never be claimed by a function in that port. Other-
wise operation is undefined.
–
Egress port control registers that normally enable the capability of a port to transmit TLPs (e.g.,
Bus Master Enable it in the PCICMD register) do not have any effect on NT Multicast TLPs emitted
by the port.
Usage Restrictions
The following is a usage restriction associated with NT multicast operation:
–
Modifying the port operating mode of a switch port configured to transmit NT multicast TLPs
requires that the Operating Mode Change Action (OMA) field in the SWPORTxCTL register be set
to reset. Note that this results in the NT Multicast Transmit Enable (NTMCTEN) bit in the port’s
NTMCC register to be cleared, thus causing the port to stop transmission of NT multicast TLPs.
Software must explicitly set the NTMCTEN bit in order to re-enable NT multicast transmission by
the port.
1.
Note that NT Multicast ECRC processing is not dependent on the setting of the ECRC Checking Enable
(ECRCCE) or ECRC Generation Enable (ECRCGE) bits in the AERCTL register of any of the port functions.
Summary of Contents for PCI Express 89HPES32NT24xG2
Page 20: ...IDT Table of Contents PES32NT24xG2 User Manual x January 30 2013 Notes...
Page 24: ...IDT List of Tables PES32NT24xG2 User Manual xiv January 30 2013 Notes...
Page 28: ...IDT List of Figures PES32NT24xG2 User Manual xviii January 30 2013 Notes...
Page 56: ...IDT PES32NT24xG2 Device Overview PES32NT24xG2 User Manual 1 20 January 30 2013 Notes...
Page 100: ...IDT Switch Core PES32NT24xG2 User Manual 4 22 January 30 2013 Notes...
Page 128: ...IDT Failover PES32NT24xG2 User Manual 6 4 January 30 2013 Notes...
Page 148: ...IDT Link Operation PES32NT24xG2 User Manual 7 20 January 30 2013 Notes...
Page 164: ...IDT SerDes PES32NT24xG2 User Manual 8 16 January 30 2013 Notes...
Page 170: ...IDT Power Management PES32NT24xG2 User Manual 9 6 January 30 2013 Notes...
Page 196: ...IDT Transparent Switch Operation PES32NT24xG2 User Manual 10 26 January 30 2013 Notes...
Page 244: ...IDT SMBus Interfaces PES32NT24xG2 User Manual 12 40 January 30 2013 Notes...
Page 247: ...IDT General Purpose I O PES32NT24xG2 User Manual 13 3 January 30 2013 Notes...
Page 248: ...IDT General Purpose I O PES32NT24xG2 User Manual 13 4 January 30 2013 Notes...
Page 330: ...IDT Switch Events PES32NT24xG2 User Manual 16 6 January 30 2013 Notes...
Page 342: ...IDT Multicast PES32NT24xG2 User Manual 17 12 January 30 2013 Notes...
Page 344: ...IDT Temperature Sensor PES32NT24xG2 User Manual 18 2 January 30 2013 Notes...
Page 384: ...IDT Register Organization PES32NT24xG2 User Manual 19 40 January 30 2013...
Page 492: ...IDT Proprietary Port Specific Registers PES32NT24xG2 User Manual 21 44 January 30 2013 Notes...
Page 588: ...IDT NT Endpoint Registers PES32NT24xG2 User Manual 22 96 January 30 2013 Notes...
Page 710: ...IDT JTAG Boundary Scan PES32NT24xG2 User Manual 25 12 January 30 2013 Notes...
Page 743: ...IDT Usage Models PES32NT24xG2 User Manual 26 33 January 30 2013 Notes...
Page 744: ...IDT Usage Models PES32NT24xG2 User Manual 26 34 January 30 2013 Notes...