PM5381-BI PMC-Sierra, Inc., PM5381-BI Datasheet - Page 520

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

13.3.3
Proprietary and Confidential to PMC-Sierra, Inc., and for its Customers’ Internal Use
Document ID: PMC-2000489, Issue 4
Transport and Path Overhead Bytes
Transport Overhead Bytes
The Transport Overhead Bytes (TOH) consist of the Section Overhead (SOH) and Line Overhead
(LOH) bytes. The S/UNI-2488 has the ability to extract these bytes from the received
SONET/SDH frame and also to insert overhead into the transmit stream. This can be done via the
RTOH and TTOH ports. See also Section 14.5 in the functional timing chapter for more
information on these ports. Note that only the first STS-12 is accessible in this manner.
Section and Line overhead can also be inserted by the TRMP as illustrated in Table 4 in Section
10.12: Transmit Regenerator Multiplexer Processor (TRMP). The TOH should always be
configured either via the TTOH port or by the insertion registers within the TRMP.
The TOH consists of the following bytes:
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·
·
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In the transmit direction, the S/UNI-2488 calculates the B1 byte over all bits of the previous
frame after scrambling. The calculated code is then placed in the current frame before
scrambling.
In the receive direction, the S/UNI-2488 calculates the B1 code over the current frame and
compares this calculation with the B1 byte received in the following frame. B1 errors are
accumulated in an error event counter.
·
·
In the transmit direction, the S/UNI-2488 inserts a fixed pointer value, with a normal new data
flag indication in the first H1-H2 pair. The concatenation indication is inserted in the remaining
H1-H2 pairs (STS-48c (STM-16c)). Pointer movements can be induced using the THPP registers.
In the receive direction, the pointer is interpreted to locate the SPE. The loss of pointer state is
entered when a valid pointer cannot be found. Path AIS is detected when H1, H2 contain an all
ones pattern.
·
A1, A2:
(STM-16c) serial stream.
J0: The J0 byte is currently defined as the STS-48c (STM-16c) section trace byte for
SONET/SDH. J0 byte is not scrambled by the frame synchronous scrambler.
Z0: The Z0 bytes are currently defined as the STS-48c (STM-16c) section growth bytes for
SONET/SDH. Z0 bytes are not scrambled by the frame synchronous scrambler.
B1: The section bit interleaved parity byte provides a section error monitoring function.
D1 - D3: The section data communications channel provides a 192 kbit/s data
communications channel for network element to network element communications.
H1, H2: The pointer value bytes locate the path overhead column in the SONET/SDH frame.
H3: The pointer action bytes contain synchronous payload envelope data when a negative
stuff event occurs. The all zeros pattern is inserted in the transmit direction. This byte is
ignored in the receive direction unless a negative stuff event is detected.
The frame alignment bytes (A1, A2) locate the SONET frame in the STS-48c
S/UNI-2488 Telecom Standard Product Datasheet
Released
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