ST70135 datasheet(13/29 Pages) STMICROELECTRONICS

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ST70135A

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ATM Specific TC Layer Functions

The 2 bytes streams (fast and slow) are received

from the byte-based processing unit. When ATM

cells are transported, this block provides basic cell

functions such as cell synchronization, cell

payload descrambling, idle/unassigned cell filter,

cell Header Error Correction (HEC) and detection.

The cell processing happens according to ITU-T

I.163 standard. Provision is also made for BER

measurements at this ATM cell level. When non

cell oriented byte streams are transported, the cell

processing unit is not active.

The interface module collects cells (from the

cell-based function module) or a Byte stream

(from the deframer). Cells are stored in FIFO’s

(424 bytes or 8 cell wide, transmit buffers have the

same size), from which they are extracted by 2

interface submodules, one providing a Utopia

level 1 interface and the other a Utopia level 2

interface.Byte stream are dumped on the SLAP

(Synchronous Link Access Protocol) interface.

Only one type of interface can be enabled in a

specific configuration.

Figure 7 : ATM Specific TC Layer Functions

Figure 8 : Interface Module

CELL SCRAMBLER

DESCRAMBLER

SYNCHRONIZER

CELL SCRAMBLER

DESCRAMBLER

SYNCHRONIZER

HEC

CELL

INSERTION/

FILTER

CELL

INSERTION/

FILTER

BER

FAST

SLOW

Interface

Module

From

Generic

SLAP

LEVEL

UTOPIA

LEVEL

UTOPIA

LEVEL

UTOPIA

LEVEL

UTOPIA

SLAP

FAST ATM

FAST BYTE STREAM

SLOW ATM

SLOW BYTE STREAM

From

ATM

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