S/UNI®-8x155 ASSP Telecom Standard Product Data Sheet
Released
10.14 SONET/SDH Path Trace Buffer (SPTB)
The SONET/SDH Section Trace Buffer (SPTB) block can handle both 64-byte CLLI messages
in SONET and 16-byte E.164 messages in SDH. This block operates similarly to the
SONET/SDH Section Trace Buffer (SSTB) except the C2 byte is also processed.
10.14.1Receive Trace Message Receiver
When TIMODE is low, the Trace Message Receiver (TMR) captures the received path trace
identifier message (J1 byte) into microprocessor readable register. It contains three pages of
trace message memory. They are the capture page, the accepted page and the expected page.
Path trace identifier data bytes from the receive stream are written into the capture page. The
expected identifier message is written 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 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.
The length of the path trace identifier message is selectable between 16 bytes and 64 bytes.
When programmed for 16 byte messages, the path 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 path 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 path trace message to be appropriately aligned for
interpretation by the microprocessor. Synchronization may be disabled, in which case, the
memory acts as a circular buffer.
When TIMODE is high, a stable message is declared when forty eight of the same path trace
identifier message (J1) bytes are received. Once in the stable state, an unstable state is declared
when one or more errors are detected in three consecutive sixteen byte windows.
10.14.2Transmit Trace Buffer
The Trace Transmit Buffer (TTB) sources the 16-byte or 64-byte trace identifier message. The
TTB contains one page of transmit trace identifier message memory. Identifier message data
bytes are written by the microprocessor into the message buffer and inserted in the transmit
stream. When the microprocessor is updating the transmit page buffer, the TTB may be
programmed to transmit null characters to prevent transmission of partial messages.
10.14.3Overhead Byte Receiver
The path signal label (PSL) found in the path overhead byte (C2) is processed. Two detection
algorithms are implemented for the declaration of path signal label mismatch.
Proprietary and Confidential to PMC-Sierra, Inc., and for its customers’ internal use.
Document No.: PMC- 2010299, Issue 2
86
PMC [ PMC-SIERRA, INC ]
