RELEASED
PMC-Sierra, Inc.
PM9311/2/3/5 ETT1™ CHIP SET
Data Sheet
PMC-2000164
ISSUE 3
ENHANCED TT1™ SWITCH FABRIC
TDM traffic operates in two of the three active states enabled and refreshing, provided the corresponding
bit in the enable_TDM_traffic register is set to 1. TDM traffic does not operate if the port is disabled. TDM
traffic and non-TDM traffic are enabled independently.
NOTE: TDM traffic does not operate while the Scheduler is in the refreshed state. So the CPU
should try to minimize the time that the Scheduler is in the refreshed state if TDM traffic is
used.
Non-TDM traffic only operates in the enabled state. When the port is in refreshing or refreshed states,
non-TDM traffic does not operate for this port: requests are not made and backpressure is asserted to
prevent other ports from sending to this port.
Table 35. Non-TDM Traffic
Scheduler
Port State
Enable non-TDM
Register
Unicast
Backpressure
Multicast
Backpressure
Disabled
Enabled
don’t care
Asserted
De-asserted
As per information from
EPP
1 (non-TDM enabled)
Not used in ETT1
Enabled
0 (non-TDM disabled)
Don’t care
Asserted
Asserted
Asserted
Asserted
Asserted
Asserted
Refreshing
Refreshed
Don’t care
Table 35 shows whether non-TDM traffic can flow, based on the port state.
NOTE: Multicast backpressure is not asserted if the port is disabled. This is to prevent head of line
blocking in the case where one port is sending a multicast cell to a port which is disabled.
See Section 1.3.4 “Multicast Traffic (subport mode)” on page 46 for more on the multicast blocking
capability.
5.3 FAULT TOLERANCE
The Scheduler reacts to link faults in different ways, depending upon the mode it is in. The mode is set by
the CRC_Action bit in the control register. This bit is set only if the Scheduler is the primary scheduler in a
dual scheduler system, otherwise it is not set.
In both modes, if a Scheduler port detects a CRC error on the incoming link from the EPP, or the link goes
down (the Ready line transitions from active to inactive for at least one clock cycle), then the port does the
following:
•
The Scheduler port is placed into the disabled state
NOTE: The Enable Port register will not reflect this change.
PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA, INC., AND FOR ITS CUSTOMERS’ INTERNAL USE
257
PMC [ PMC-SIERRA, INC ]
