PMC-Sierra, Inc.
PRELIMINARY
PM5381 S/UNI-2488
DATASHEET
PMC-2000489
ISSUE 1
SATURN USER NETWORK INTERFACE FOR 2488 MBIT/S
10.2 SONET/SDH Receive Line Interface (SRLI)
The SONET/SDH receive line interface block performs byte and frame alignment on the incoming
2488 Mbit/s data stream based on the SONET/SDH A1/A2 framing pattern.
While out of frame, the SRLI monitors the receive data stream for an occurrence of the A1/A2
framing pattern. The SRLI adjusts its byte and frame alignment when three consecutive A1 bytes
followed by three consecutive A2 bytes occur in the data stream. The SRLI informs the RRMP
framer block when the framing pattern has been detected to reinitialize to the new transport frame
alignment. While in frame, the SRLI maintains the same byte and frame alignment until the
RRMP declares out of frame.
10.3 Receive Regenerator and Multiplexor Processor (RRMP)
The Receive Regenerator and Multiplexor Processor (RRMP) block extracts and process the
transport overhead of the received data stream.
The RRMP frames to the data stream by operating with an upstream pattern detector (SRLI) that
searches for occurrences of the A1/A2 framing pattern. Once the SRLI has found an A1/A2
framing pattern, the RRMP monitors for the next occurrence of the framing pattern 125µs later.
Two framing pattern algorithms are provided to improve performance in the presence of bit errors.
In algorithm 1, the RRMP declares frame alignment (removes OOF defect) when the 12 A1 and
the 12 A2 bytes are seen error-free in the first STS-12 (STM-4) of the STS-48c (STM-16-16c)
stream. In algorithm 2, the RRMP declares frame alignment (removes OOF defect) when only
the last A1 byte and the first four bits of the first A2 byte are seen error-free in the first STS-12
(STM-4) of the STS-48c (STM-16c) . Once in frame, the RRMP monitors the framing pattern and
declares OOF when one or more bit errors in the framing pattern are detected for four
consecutive frames. Again, depending upon the algorithm either 24 framing bytes or 12 framing
bits are examined for bit errors in the framing pattern.
The performance of these framing algorithms in the presence of bit errors and random data is
robust. When looking for frame alignment the performance of each algorithm is dominated by the
alignment algorithm used in the SRLI which always examines 3 A1 and 3 A2 framing bytes. The
probability of falsely framing to random data is less than 0.00001% for either algorithm. Once in
frame alignment, the RRMP continuously monitors the framing pattern. When the incoming
-3
stream contains a 10 BER, the first algorithm provides a 99.75% probability that the mean time
between OOF occurrences is 1.3 seconds and the second algorithm provides a 99.75%
probability that the mean time between OOF occurrences is 7 minutes.
The RRMP also detects loss of frame (LOF) defect and loss of signal (LOS) defect. LOF is
declared when an out of frame (OOF) condition exists for a total period of 3ms during which there
is no continuous in frame period of 3 ms. LOF output is removed when an in frame condition
exists for a continuous period of 3 ms. LOS is declared when a continuous period of 20 µs
without transitions on the received data stream is detected. LOS is removed when two
consecutive framing patterns are found (based on algorithm 1 or algorithm 2) and during the
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