Released
Datasheet
PM73487 QRT
PMC-Sierra, Inc.
PMC-980618
Issue 3
622 Mbps ATM Traffic Management Device
3.2.3.15 BP_ACK Remote Failure Detection
A missing or corrupted (bad second inversion) backpressure packet is reported to the
microprocessor by the BP_REMOTE_FAIL flag (refer to “BP_REMOTE_FAIL” on
page 112). The BP_REMOTE_FAIL flag is an indication of a broken cell path at the
ingress QRT. A missing or corrupted acknowledgment packet is reported to the micropro-
cessor by the ACK_LIVE_FAIL (refer to “ACK_LIVE_FAIL” on page 111).
3.2.3.16 Detection Hysteresis
If the fault detected is the result of a missing or bad background pattern, it takes the QRT a
minimum of 8 and a maximum of 12 switch fabric clocks to recover after the pattern has
been restored. If a backpressure packet is withheld or detected as bad during a cell time
because of built-in hysteresis, it takes two valid backpressure packets in successive cell
times for the QRT to recover. If an acknowledgment packet is detected as bad, it takes one
cell time for the QRT to recover.
3.2.4 Tables of Switch Fabric Interface Failure Behaviors
3.2.4.1 IRT-to-Switch Fabric Interface
In Figure 48 on page 44, the IRT interface consists of a and b. In the figure, a refers to each of the
four SE_SOC_OUT and SE_D_OUT#(3:0) data ports, while b refers to the corresponding
BP_ACK_IN signals in the QRT. Table 2 summarizes the failure conditions detected by the IRT
on b and the actions taken.
Table 2. Failure Conditions, IRT-to-Switch Fabric Interface
Fault Detected On b
Action Taken
Comment
Cannot lock to special coding and
guaranteed transitions on
BP_ACK_IN.
Idle cells are sent out on data interface a.
Internally to the IRT, cells that would have gone
out are ACKed if all ports are failing; else they are line.
ONACKed. No multicast cells are generated for
the port. BP_ACK_FAIL (refer to
Port treated as dead. Problem is
probably with the BP_ACK_IN
“BP_ACK_FAIL” on page 112) signaled to the
microprocessor.
No backpressure received on
BP_ACK_IN.
Idle cells are sent out on data interface a. Inter-
nally to the IRT, cells that would have gone out
are ACKed if all ports fail; else they are
ONACKed. No multicast cells are generated for
the port. BP_REMOTE_FAIL (refer to
“BP_REMOTE_FAIL” on page 112) signaled to
the microprocessor.
Port treated as dead. Problem is
with the forward data flow, and the
QSE is signaling this back to the
IRT.
No ACK, MNACK, or ONACK
Cell that was transmitted is treated as sent.
received, although unicast cell is sent ACK_LIVE_FAIL (refer to “ACK_LIVE_FAIL”
out. on page 111) signaled to the microprocessor.
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PMC [ PMC-SIERRA, INC ]
