PM5381-BI PMC-Sierra, Inc., PM5381-BI Datasheet - Page 77

• Manufacturer Part Number: PM5381-BI
• Description: ATM UNI, Single Channel ATM PHY Interface for 2488.32Mbps
• Manufacturer: PMC-Sierra, Inc.

Proprietary and Confidential to PMC-Sierra, Inc., and for its Customers’ Internal Use
Document ID: PMC-2000489, Issue 4
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 first A1 byte and the first four bits of the last 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 stream contains a 10
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
intervening time (one frame) there are no continuous periods of 20 µs without transitions on the
received data stream.
The RRMP calculates the section BIP-8 error detection code on the scrambled data of the
complete 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 STS-1 (STM-0) #1 of the following frame after de-scrambling. Any difference indicates a
section BIP-8 error. The RRMP accumulates section BIP-8 errors in a microprocessor readable
16-bit saturating counter (up to 1 second accumulation time). Optionally, block section BIP-8
errors can be accumulated.
The RRMP optionally de-scrambles the received data stream.
The RRMP calculates the line BIP-8 error detection codes on the de-scrambled line overhead and
synchronous payload envelope bytes of the constituent STS-1 (STM-0). The line BIP-8 code is
based on a bit interleaved parity calculation using even parity. The calculated BIP-8 codes are
compared with the BIP-8 codes extracted from the B2 byte of the constituent STS-1 (STM-0) of
the following frame after de-scrambling. Any difference indicates a line BIP-8 error. The RRMP
accumulates line BIP-8 errors in a microprocessor readable 24 bits saturating counter (up to 1
second accumulation time). Optionally, block BIP errors can be accumulated.
-3
BER, the first algorithm provides a 99.75% probability that the
S/UNI-2488 Telecom Standard Product Datasheet
Released
77