cx29600 Mindspeed Technologies, cx29600 Datasheet - Page 80

• Manufacturer Part Number: cx29600
• Description: Optiphytm - M155 Sts-3 Sonet/sdh Multiplexer
• Manufacturer: Mindspeed Technologies

2.0 Functional Description
2.4 SONET/SDH Framer and Overhead Processor
2.4.5 Custom Extensions
2.4.6 SONET Frame Scrambler
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Several of the control register bits in the CX29600 register map are for specific
applications when CX29600 is used with the Broadband Access Mapper (BAM)
device. These bits may be of use in other applications but may also generate
operation that does not conform to SONET standards. This is not a problem when
used with BAM, since BAM is a termination device and thus the non-standard
data contained is only visible between CX29600 and BAM. The BAM-specific
bits are listed below:
Each SONET Network Element (NE) is required to have the capability to derive
the clock timing from the incoming line interface signal. All transmitted line
interface signals are timed from this clock. Therefore, it is important to maintain
the ones density in the data stream to ensure enough data transitions for robust
clock recovery. The technique commonly used with modems, called scrambling
and descrambling, is used in SONET to make the data appear to be more random.
127, operating at the line rate. The generating polynomial is x
scrambler is reset to 1111111 on the most-significant bit of the J1 byte. This bit
and all the subsequent bits to be scrambled are added, modulo 2, to the output
from the x
overhead is scrambled.
in register TXSEC to send all zeros after scrambling.
• DOWNALM bit 2—copies the H1/H2 pointer bytes from the first STS-1
• DOWNALM bit 1—allows generation of AIS-P downstream upon
This process uses a frame synchronous scrambler with a sequence length of
Set bit 7 in register TXSEC to disable transmitter frame scrambling. Set bit 1
Set bit 3 in register DOWNALM to disable receiver frame scrambling.
position to the second and third STS-1 positions. This is used to provide
the pointer information to independent BAM slices that observe data in the
second and third STS-1 positions since they do not have visibility of the
first position pointer. An example of this is the VC-4 to TUG-3 mapping
for SDH. The H4 byte is also copied in the same manner when this bit is
set. This feature is disabled by default.
reception of PLM-P or Uneq-P. Usually downstream AIS-P is generated
only upon reception of LOP-P. BAM performs path conditioning and
generates upstream alarms for PLM-P and Uneq-P the same as when it
receives AIS-P or LOP-P. Generating this downstream alarm in CX29600
removes the requirement of separate notification to BAM of reception of
PLM-P or Uneq-P since BAM has the capability to detect AIS-P. This
feature is disabled by default.
Mindspeed Technologies
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position of the scrambler. Everything but the first row of the section
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CX29600 Data Sheet
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29600-DSH-001-B
+ x
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+ 1. The
CX29600