DS2155 datasheet(167/262 Pages) DALLAS

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DS2156

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24.

UTOPIA BACKPLANE INTERFACE

24.1 Description

The DS2156’s UTOPIA interface maps the ATM cells in a T1/E1 frame in the transmit direction as per

ATM Forum Specifications af-phy-0016.000 [1] and af-phy-0064.000 [2] and recovers them in the

receive direction from a similar mapping. In the receive direction, the cell delineation mechanism used

for finding ATM cell boundaries within a T1/E1 frame is performed as per ITU-T I.432 [4]. The terms

“physical layer (PHY)” and “line side” are used synonymously in this document and refer to the device

interface with the line side of the DS2156. The terms “ATM layer” and “system side” are used

synonymously and refer to the UTOPIA-II interface of the DS2156.

The transmit section receives cells from the ATM layer through the UTOPIA-II interface. It writes the

cells into a 4-cell-deep transmit FIFO that is used for rate decoupling. The FIFO’s depth is programmable

to two, three, or four ATM cells. The cells are mapped into the T1/E1 frame as per [1] and [2]. The

DS2156 can be configured to perform valid HEC insertion and payload scrambling.

The receive section delineates the cells from the data received from the PHY layer as per [4]. Once cells

are delineated, they are written into a 4-cell-deep receive FIFO used for rate decoupling. The receive

section interfaces with the ATM layer through the UTOPIA-II interface. It can also be configured to

perform payload descrambling and idle/unassigned cell filtering. Single-bit HEC error correction is also

supported.

24.1.1

List of Applicable Standards

1) ATM Forum “DS1 Physical Layer Specification,” af-phy-0016.000, September 1994

2) ATM Forum “E1 Physical Layer Specification,” af-phy-0064.000, September 1996

3) ATM Forum “UTOPIA Level 2 Specification,” Version 1.0, af-phy-0039.000, June 1995

4) B-ISDN User-Network Interface—Physical Layer Specification—ITU-T Recommendation I.432–

03/93

24.1.2

Acronyms and Definitions

ACRONYM

DEFINITION

ATM

Asynchronous Transfer Mode

CRC

Cyclic Redundancy Check

HEC

Header Error Check

LCD

Loss-of-Cell Delineation

OAM

Operations Administration and Maintenance

OCD

Out-of-Loss Delineation

PMON

Performance Monitoring

UTOPIA

Universal Test and Operations PHY Interface for ATM

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