Released
PMC-Sierra, Inc.
PM9311/2/3/5 ETT1™ CHIP SET
Data Sheet
PMC-2000164
ISSUE 3
ENHANCED TT1™ SWITCH FABRIC
Figure 41. Simple Non-Redundant Scheduler Configuration
Enhanced
Port Processor 1
Enhanced
Port Processor 2
Scheduler 0
1.9.2.2 Redundant Configurations
For a redundant Crossbar configuration, the redundant connection provides the uncorrupted information
between the Dataslice and Crossbar. In Figure 42, Dataslice 1 and Dataslice 2 are connected to both
Crossbar 0 and Crossbar 1. The same information is sent from the Dataslices to each of the Crossbars,
and therefore, the same information is received by the Dataslices from each of the Crossbars.
Consider when a CRC error occurs from Dataslice 1 to Crossbar 0, and no CRC error occurs from
Dataslice 1 to Crossbar 1. In this situation, Dataslice 2 will receive invalid information from Crossbar 0, but
will receive valid information from Crossbar 1. Dataslice 2 uses the valid information and no cells are
corrupted. Crossbar 0 will indicate to the CPU that a CRC error has occurred.
If a CRC error occurs from Crossbar 0 to Dataslice 2, Dataslice 2 would not receive valid information from
Crossbar-0. Since Crossbar 1 receives the same information as Crossbar 0, Dataslice 2 will get the valid
information from Crossbar 1. Dataslice-2 uses the valid information and no cells are corrupted. Dataslice 2
will indicate to the CPU that a CRC error has occurred.
In both situations, the simple redundant Crossbar configuration has prevented cell loss in the event of a
single CRC error. The occurrence of a CRC error between the Dataslice and Crossbar is always noted, but
no corrective action is required.
Figure 42. Simple Redundant Crossbar Configuration
Crossbar 0
Dataslice 1
Dataslice 2
Crossbar 1
PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA, INC., AND FOR ITS CUSTOMERS’ INTERNAL USE
95
PMC [ PMC-SIERRA, INC ]
