
IDT Multicast
PES32NT24xG2 User Manual
17 - 4
January 30, 2013
Notes
Since bits in the multicast base address that correspond to the multicast group number or are less than
the multicast index position (i.e., INDEXPOS) must be zero, the multicast group ID associated with a TLP
may be determined as shown in Figure 17.2.
–
For the purpose of multicast TLP determination, address bits in the TLP address less than the
multicast index position and bits associated with the multicast group ID are zeroed. This address
is then compared to the multicast base address. If the two are not equal, then the TLP is not a
multicast TLP.
–
If the two addresses are equal, then the multicast group ID is extracted from the address bits that
correspond to enabled multicast groups. The number of bits is equal to
log
2
(NU 1)
and start with the address bit corresponding to the value of INDEXPOS.
–
If the multicast group ID is greater than NUMGROUP, then the TLP is not a multicast TLP. Other-
wise, the TLP is a multicast TLP.
Figure 17.2 Multicast Group Address Region Determination
Once a TLP has been determined to be a multicast TLP and the multicast group ID has been deter-
mined, the following error checks are performed.
–
If the multicast TLP fails the source validation ACS check, then it is handled as specified by ACS.
No other ACS checks are performed on multicast TLPs.
–
Associated with each multicast group is a “block all” bit. If the block all bit corresponding to the
multicast group ID associated with a received multicast TLP is set in the ingress port, then the
multicast TLP is treated as a blocked multicast TLP. The block all bits are contained in the ingress
port’s Multicast Block All (MCBLKALL) fields of the Multicast Block All Low (MCBLKALLL) and
Multicast Block All High (MCBLKALLH) registers.
–
Associated with each multicast group is a “block untranslated” bit. If the block untranslated bit
corresponding to the multicast group ID associated with a received multicast TLP is set in the
ingress port and the TLP is untranslated, as determined by the Address Type (AT) field in the TLP
header, then the multicast TLP is treated as a blocked multicast TLP. The block untranslated bits
are contained in the ingress port’s Multicast Block Untranslated (MCBLKUT) fields of the Multicast
Block Untranslated Low (MCBLKUTL) and Multicast Block Untranslated High (MCBLKUTH) regis-
ters.
–
A blocked multicast TLP is treated in the following manner.
• The TLP is dropped and flow control credits are returned.
• The error is reported to AER as a MC Blocked TLP error and the header is logged.
• In an upstream port, the Signaled Target Abort (STAS) bit is set in the PCI Status (PCISTS)
register.
• In a downstream switch port, the Signaled Target Abort (STAS) bit is set in the Secondary Status
(SECSTS) register.
–
Note that the “block all” and “block untranslated” functions are performed at the ingress port on
which the multicast TLP was received.
A received multicast TLP without errors is forwarded to egress ports as described in the next section.
M u tic a st B a s e A d d re ss
M u ltic a s t G ro u p O ffs e t
A d d re s s
M u ltic a st
G ro u p ID
M u ltic a st
In d e x
P o s itio n
Содержание PCI Express 89HPES32NT24xG2
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