S/UNI®-8x155 ASSP Telecom Standard Product Data Sheet
Released
While out of frame, the RAPS block monitors the bit-serial APS data stream for an occurrence
of the framing pattern (A1, A2). The RAPS informs the RAOP Framer block when three A1
bytes followed by three A2 bytes has been detected to reinitializes the frame byte counter to the
new alignment. The Framer block declares frame alignment on the next SONET/SDH frame
when either all A1 and A2 bytes are seen error-free or when only the first A1 byte and the first
four bits of the last A2 byte are seen error-free depending upon the selected framing algorithm.
Once in frame, the Framer block monitors the framing pattern sequence and declares out of
frame (OOF) when one or more bits errors in each framing pattern are detected for four
consecutive frames. Again, depending upon the algorithm either all framing bytes are examined
for bit errors each frame, or only the first A1 byte and the first four bits of the last A2 byte are
examined for bit errors each frame.
10.22.2 Descramble
The Descramble Block utilizes a frame synchronous descrambler to process the receive stream.
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The generating polynomial is x + x + 1 and the sequence length is 127. Details of the
descrambling operation are provided in the references. Note that the framing bytes (A1 and A2)
are not descrambled. A register bit is provided to disable the descrambling operation.
10.22.3Data Link Extract
The section DCC bytes (D1, D2 and D3) are used to indicate transport alarm (section and/or
line alarms) status of the path data stream. When 3 of 5 bits of the DCC data stream are high,
the path data stream is in transport alarm condition (LOS, LOF, LAIS, LRDI or LOP). When 3
of 5 bits of the DCC data stream are low, the path data stream is not in alarm condition.
When the APS path data stream is used by the transmit serial interface (transmit path bridged
from a remote S/UNI-8x155 to a transmit channel), a transport alarm will cause path AIS to be
inserted in the transmit direction.
When the APS path data stream is terminated by the receive serial interface (receive path from a
remove S/UNI-8x155 selected by a receive channel), a transport alarm will affect the
AUTOPRDI function in the path transmit direction.
10.22.4Error Monitor
The Error Monitor Block calculates the received section BIP-8 error detection code (B1) based
on the scrambled data of the complete SONET/SDH frame. The section BIP-8 code is based on
a bit interleaved parity calculation using even parity. The calculated BIP-8 code is compared
with the BIP-8 code extracted from the B1 byte of the following frame. Differences indicate
that a section level bit error has occurred. Up to 64000 (8 x 8000) bit errors can be detected per
second.
The Error Monitor Block accumulates these section level bit errors in a 16-bit saturating counter
that can be read via the microprocessor interface. Circuitry is provided to latch this counter so
that its value can be read while simultaneously resetting the internal counter to 0 or 1, if
appropriate, so that a new period of accumulation can begin without loss of any events. It is
intended that this counter be polled at least once per second so as not to miss bit error events.
Proprietary and Confidential to PMC-Sierra, Inc., and for its customers’ internal use.
Document No.: PMC- 2010299, Issue 2
96
PMC [ PMC-SIERRA, INC ]
