
IDT Switch Core
PES32NT24xG2 User Manual
4 - 6
January 30, 2013
Notes
Packet Ordering
The PCI Express Base Specification 2.1 contains packet ordering rules to ensure the producer/
consumer model is honored across a PCI Express hierarchy and to prevent deadlocks.
–
The switch honors the strict and relaxed ordering rules defined in the PCI Express Base Specifi-
cation.
–
The switch does not support the ID-Based Ordering (IDO) rules defined in the PCI Express Base
Specification.
The switch core performs packet ordering on a per-port basis, at the output of the ingress and egress
buffers of each port. Table 4.4 shows the ordering rules honored by the switch core.
Arbitration
Packets stored in the ingress buffer of each port are subject to arbitration as they are moved towards the
target egress port. The switch core performs all packet arbitration functions in the PES32NT24xG2. The
following sub-sections describe these in detail.
Port Arbitration
Figure 4.2 shows the architectural model of port arbitration.
Row Pass Column?
Posted
Request
Non-Posted Request
Completion
Memory
Write or
Message
Request
Read
Request
IO or
Configura
tion Write
Request
Read
Comple-
tion
IO or
Configura
tion Write
Comple-
tion
Posted
Request
Memory
Write or Mes-
sage
Request
No
Yes
Yes
Yes
Yes
Non Posted
Request
Read
Request
No
No
No
Yes
Yes
IO or Config-
uration Write
Request
No
No
No
Yes
Yes
Completion
Request
Read Com-
pletion
‘Yes’ if
packet has
RO bit set;
Else ‘No’
Yes
Yes
No
No
IO or Config-
uration Write
Completion
Yes
Yes
No
No
Table 4.4 Packet Ordering Rules in the PES32NT24xG2
Содержание PCI Express 89HPES32NT24xG2
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