PM5342 Datasheet, PDF (133/558 Pages) PMC-Sierra, Inc – SONET/SDH Payload Extractor/Aligner

DATA SHEET
PMC-970133
ISSUE 4
PM5342 SPECTRA-155
SONET/SDH PAYLOAD EXTRACTOR/ALIGNER
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 serial to
parallel converter which always examines all framing bits. The probability of
falsely framing to random data is less than 0.00001% for either algorithm. Once
in frame alignment, the SPECTRA-155 continuously monitors the framing
pattern. When the incoming stream contains a 10^-3 BER, the first algorithm
provides a mean time between OOF occurrences of 33 minutes in STS-1
(STM-0/AU3) mode and 26 seconds in STS-3/3c (STM-1/AU3/AU4) mode. The
second algorithm provides a mean time between OOF occurrences of 103
minutes, regardless of operating mode.
The RSOP block provides descrambled data and frame alignment indication
signals for use by the Receive Line Overhead Processor.
9.3 Receive Section Trace Buffer
The receive portion of the SONET/SDH Section Trace Buffer captures the
received section trace identifier message (J0 byte) into microprocessor readable
registers. It contains two pages of trace message memory. One is designated
the capture page and the other the expected page. Section trace identifier data
bytes from the receive stream are written into the capture page. The expected
identifier message is downloaded by the microprocessor into the expected page.
On receipt of a trace identifier byte, it is written into next location in the capture
page. The received byte is compared with the data from the previous message
in the capture page. An identifier message is accepted if it is received
unchanged three times, or optionally, five times. The accepted message is then
compared with the expected message. If enabled, an interrupt is generated
when the accepted message changes from matching to mismatching the
expected message and vice versa. If the current message differs from the
previous message for eight consecutive messages, the received message is
declared unstable. The received message is declared stable when the received
message passes the persistency criterion (three or five identical receptions) for
being accepted. An interrupt may be optionally generated on entry to and exit
from the unstable state. Optionally, line AIS may be inserted in the received
stream when the receive message is in the mismatched or unstable state.
The length of the section trace identifier message is selectable between 16 bytes
and 64 bytes. When programmed for 16 byte messages, the section trace buffer
synchronizes to the byte with the most significant bit set to high and places the
byte at the first location in the capture page. When programmed for 64 byte
messages, the section trace buffer synchronizes to the trailing carriage return
(CR = 0DH), line feed (LF = 0AH) sequence and places the next byte at the
head of the capture page. This enables the section trace message to be
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