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S/UNI-QUAD
PMC-Sierra, Inc.
PM5349 S/UNI-QUAD
DATASHEET
PMC-971239 ISSUE 6 SATURN USER NETWORK INTERFACE (155-QUAD)
Proprietary and Confidential to PMC-Sierra, Inc., and for its Customers’ Internal Use
34
While in-frame, the framing bytes (A1, A2) in each frame are compared against
the expected pattern. Out-of-frame is declared when four consecutive frames
containing one or more framing pattern errors have been received.
While out-of-frame, the SIPO block monitors the receive stream for an occurrence
of the framing pattern. When a framing pattern is recognized, the Framer block
verifies that an error free framing pattern is present in the next frame before
declaring in-frame.
10.2.2
Descramble
The Descramble Block utilizes a frame synchronous descrambler to process the
receive stream. The generating polynomial is x
7
+ x
6
+ 1 and the sequence
length is 127. Details of the de-scrambling operation are provided in the
references. Note that the framing bytes (A1 and A2) and the trace/growth bytes
(J0/Z0) are not descrambled. A register bit is provided to disable the de-
scrambling operation.
10.2.3
Error Monitor
The Error Monitor Block calculates the received section BIP-8 error detection
code (B1) based on the scrambled data of the complete STS-3c (STM-1) frame.
The section BIP-8 code is based on a bit interleaved parity calculation using even
parity. Details are provided in the references. The calculated BIP-8 code is
compared with the BIP-8 code extracted from the B1 byte of the following frame.
Differences indicate that a section level bit error has occurred. Up to 64000 (8 x
8000) bit errors can be detected per second. The Error Monitor Block
accumulates these section level bit errors in a 16-bit saturating counter that can
be read via the microprocessor interface. Circuitry is provided to latch this
counter so that its value can be read while simultaneously resetting the internal
counter to 0 or 1, if appropriate, so that a new period of accumulation can begin
without loss of any events. It is intended that this counter be polled at least once
per second so as not to miss bit error events.
10.2.4
Loss of Signal
The Loss of Signal Block monitors the scrambled data of the receive stream for
the absence of 1's. When 20 ± 3 µs of all zeros patterns is detected, a loss of
signal (LOS) is declared. Loss of signal is cleared when two valid framing words
are detected and during the intervening time, no loss of signal condition is
detected. The LOS signal is optionally reported on the RALRM output pin when
enabled by the LOSEN Receive Alarm Control Register bit.