Released
Datasheet
PM73487 QRT
PMC-Sierra, Inc.
PMC-980618
Issue 3
622 Mbps ATM Traffic Management Device
port called ACK_LIVE_FAIL and BP_REMOTE_FAIL (refer to “ACK_LIVE_FAIL”
and to “BP_REMOTE_FAIL” on page 112) that check the ACK response from the switch
fabric and the liveness of the data line. The liveness signal alone will not determine that a
QSE is faulty.
3.2.3.13 BP_ACK_IN Pattern Checking
Backpressure and acknowledgment are transmitted from the egress QRT to the ingress
QRT in packets on the BP_ACK_OUT line. The format of the packets is as follows:
A background pattern “0000111100001. . .”
Generated by the QRT at egress and propagated by the QSE. This pattern is
checked at the ingress QRT.
First Inversion (of the background pattern)
Indicates the beginning of the packet.
Mode
Indicates the nature of the packet (that is, acknowledge or backpressure).
Data1
Indicates the Most Significant Bit (MSB) of data.
Data0
Indicates the Least Significant Bit (LSB) of data for acknowledgment - The second
bit of data for backpressure.
Second Inversion
Verify the first inversion was not a glitch and the fabric is not stuck.
Code Ext1
The LSB of the backpressure data; otherwise, it must be “0” for acknowledgment
to be accepted as valid.
Code Ext0
Must be “0” to be accepted as valid. This is reserved for future use.
If any part of the coding is missing or inconsistent, the BP/ACK path is indicated as bad
by asserting the BP_ACK_FAIL interrupt (refer to “BP_ACK_FAIL” on page 112).
3.2.3.14 BP_ACK Inversion Checking
The first inversion and the second inversion in the packet are separated by three bits to
ensure a fabric fault, such as stuck at “1” or “0”, or a glitch will not result in a false packet.
If the second inversion is not consistent (inverse) with the first inversion, a bad path is
indicated by asserting the BP_ACK_FAIL interrupt (refer to “BP_ACK_FAIL” on
page 112).
When the BP/ACK path is determined to be bad, the ingress QRT withholds issuing valid
cells and instead transmits idle cells until the fabric recovers from the fault.
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PMC [ PMC-SIERRA, INC ]
