M28529G-12 Mindspeed Technologies, M28529G-12 Datasheet - Page 109

• Manufacturer Part Number: M28529G-12
• Description: ATM IMA 8.192Mbps 1.8V/3.3V 484-Pin BGA
• Manufacturer: Mindspeed Technologies

Specifications of M28529G-12

• Package: 484BGA
• Utopia Type: Level 2
• Typical Operating Supply Voltage: 1.8|3.3 V
• Minimum Operating Supply Voltage: 1.71|3.135 V
• Maximum Operating Supply Voltage: 1.89|3.465 V
• Maximum Output Rate: 8.192 Mbps

Table 1-27.
Table 1-28.
1.14.2.4
The ATM standard requires cell scrambling to ensure that only valid headers are found in the cell delineation
process. Scrambling randomizes any repeated patterns or other data strings that could be mistaken for valid
headers. The M2852x supports two types of scrambling as defined by ITU-T I.432:
1. Self Synchronizing Scrambler (SSS)
2. Distributed Sample Scrambler (DSS). Typically, SSS is used and is, therefore, the M2852x’s default method.
1.14.2.4.1
SSS scrambling uses the polynomial ×
can be enabled in EnTxCellScr, bit 5, of the CGEN register (0x08).
Descrambling uses the same polynomial to recover the 48-byte cell payload. It can be enabled in EnRxCellScr, bit
4, of the CVAL register (0x0C).
1.14.2.4.2
DSS scrambling uses the ×
calculated after the first four bytes of the header have been scrambled. DSS scrambling is enabled in EnTxDSSScr,
bit 1, of the CGEN register (0x08).
Descrambling uses the first six bits of the HEC for alignment. Once alignment is found, all eight bits of the HEC are
sampled. Descrambling uses the same polynomial to recover the 48-byte cell payload. It is enabled in
EnRxDSSScr, bit 0, of the CGEN register (0x08). If DSS descrambling fails, the M2852x defaults to unscrambled
mode.
28529-DSH-001-K
Receive Cell Mask Bit
However, xDSL in asynchronous format generally use DSS.
Match
Match
Cell
Fail
Fail
0
0
0
0
1
Cell Screening—Matching
Cell Screening—Accept/Reject Cell
NOTE:
Cell Scrambler
SSS Scrambling
DSS Scrambling
Receive Cell Header Bit
31
Reject Header
If both SSS and DSS are enabled, SSS overrides DSS.
+ ×
28
0
0
1
1
0
1
x
0
1
+ 1 polynomial to scramble the entire cell, except the HEC byte. HEC is
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+ 1 to scramble the payload, leaving the five header bytes untouched. It
Accept Cell
Reject Cell
Reject Cell
Accept Cell
Incoming Bit
Result
0
1
0
1
x
Match
Fail
Fail
Match
Match
®
Result
Functional Description
94