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Notes
PES48H12G2 User Manual
®
Introduction
The PES48H12G2 implements multicast within switch partitions as defined by the PCI-SIG Multicast
ECN. The multicast capability enables a single TLP to be forwarded to multiple destinations. The destina-
tions to which a multicast TLP is forwarded are referred to as a multicast group.
– A multicast group may contain zero or more destinations.
The PES48H12G2 supports up to 64 multicast groups -- this is the maximum allowed by the PCIe stan-
dard.
– The number of supported groups is advertised via the MAXGROUP field in the MCCAP register.
The default value of this field corresponds to 32 groups. This field may be re-programmed during
initial switch configuration (e.g., EEPROM) to advertise up to 64 groups.
A function need not be a member of a multicast group in order generate a multicast TLP that is
forwarded to a multicast group. For example, any endpoint or root may generate a multicast TLP by trans-
mitting a posted TLP with an address that maps to a multicast group.
Multicast is only supported within a PES48H12G2 switch partition. No mechanism exists for a multicast
TLP to cross from one partition to another. Multicast is compatible with legacy PCIe roots and endpoints.
Addressing and Routing
Multicast addressing and routing may be partitioned into the task of determining that a TLP is a multicast
TLP, routing a multicast TLP to functions (e.g.,
cast egress processing performed at each function. These tasks are described in the following sections.
Multicast TLP Determination
The determination of whether or not a TLP is a multicast TLP is made by functions that receive the TLP.
All functions associated with a PES48H12G2 switch partition are expected to have identical multicast
routing configuration. Thus, multicast TLP determination may be made using register values associated
with the capability structure of any function in the partition.
– Modification of multicast routing fields requires that multicast traffic be quiesed.
The following multicast register fields must be configured to the same value in all functions associated
with a switch partition. Violating this requirement results in undefined behavior on receipt of a multicast TLP.
Non-multicast TLPs are not affected.
Register: MCCTL, field: NUMGROUP
Register: MCBARL, fields: INDEXPOS, MCBARL
Register: MCBARH, field: MCBARH
Unless otherwise noted, TLP processing associated with a multicast TLP is the same as that for any
other TLP. For example, malformed checks are the same, poison bit processing is the same, ECRC
checking and error reporting is the same, etc. When the Multicast Enable (MEN) bit is cleared in the Multi-
cast Control (MCCTL) register, multicast is disabled and no TLP received on the link associated with that
partition is a multicast TLP. A TLP determined not to be a multicast TLP is routed using traditional unicast
PCIe routing rules. Thus, unroutable "multicast TLPs" are handled in the same manner as any other
unroutable TLP.
bridges associated with egress ports), and multi-
PCI-to-PCI
14 - 1
Chapter 14
Multicast
April 5, 2013
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