Released
Datasheet
PM73487 QRT
PMC-Sierra, Inc.
PMC-980618
Issue 3
622 Mbps ATM Traffic Management Device
3.2.3.6 Forced Bad Parity
The header parity detection logic can be checked by clearing the P bit in the
RX_CH_TAG word (refer to “RX_CH_TAG” on page 185). This forces bad parity (even
parity) to be created.
3.2.3.7 Marked Cell Counting
The Mark Bit (MB) in the RX_CH_TAG word (refer to “RX_CH_TAG” on page 185) is
set and it is sent between the QRT and QSE. If ACK or NO_RESP feedback is received,
the RX_MARKED_CELLS counters count enabled cells (modulo 16) at the ingress QRT.
The TX_MARKED_CELLS counters count marked cells (modulo 16) that are received at
the egress QRT. The RX_MARKED_CELLS and TX_MARKED_CELLS counters (refer
to “MARKED_CELLS_COUNT” on page 110) help identify subtle failures in the fabric
and can be used to create strong diagnostic routines. These counters are separate for all
four switch fabric interfaces in each of the transmit and receive directions.
3.2.3.8 Remote Data Path Failure Indication
When a cell path is determined to be bad, the egress QRT indicates a remote failure by
violating the syntax of the BP_ACK_OUT signal. This is an indication to the ingress QRT
that a fabric fault in the forward cell path has been detected. Also, an
SE_INPUT_PORT_FAIL interrupt (refer to “SE_INPUT_PORT_FAIL” on page 112) is
flagged to the microprocessor. The cell being received at this time is discarded. This is
detected as a BP_REMOTE_FAIL (refer to “BP_REMOTE_FAIL” on page 112) by the
QRT or QSE on the other end of the link. Withholding backpressure from the ingress QRT
prompts it to send only idle cells on the forward cell path until it recognizes a valid back-
pressure pattern again.
3.2.3.9 Unacknowledged Cell Detection
If no acknowledgment is received for a cell, the ACK_LIVE_FAIL interrupt (refer to
“ACK_LIVE_FAIL” on page 111) is asserted. This is an indication of a problem in the
end-to-end path through the switch fabric.
3.2.3.10 Switch Fabric Loopback
The internal loopback feature also helps detect and isolate fabric faults. When dribbling
errors or other faults are detected, internal loopback can help isolate the fault.
3.2.3.11 Fabric Clock Failure Detection
The switch fabric interface contains a clock failure detection circuit. The detection circuit
samples the fabric clock with the high-frequency system clock and determines whether or
not it possess signal changes. If the clock failure detection circuit is tripped, an interrupt is
signaled at the processor interface.
3.2.3.12 Liveness of Backpressure Signal
The backpressure signal is checked for a “10” pattern at the start of the backpressure sig-
nal. For each of the QSEs, the QRT has a Backpressure (BP) liveness indication bit called
BP_ACK_FAIL (refer to “BP_ACK_FAIL” on page 112). There are two bits per QSE
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PMC [ PMC-SIERRA, INC ]
