MT90221 Просмотр технического описания (PDF) - Mitel Networks

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MT90221

Quad IMA/UNI PHY Device

Mitel Networks 

MT90221

ATM In

UTOPIA L2 Interface

Cell_In_Control

Transmitter

Cell RAM

FIFO Link 0

(see Note 1)

FIFO Link 1

(see Note 1)

ICP Cell Modifier and

Cell Scrambling

P/S

ICP Cell Modifier and

Cell Scrambling

P/S

Serial

Streams

Link 0

Link 1

from IDCR Generator

Micro I/F

FIFO Link 3

(see Note 1)

TX Utopia FIFO

Group 0

ICP Cell Modifier and

Cell Scrambling

P/S

TX Utopia FIFO

Group 3

Round Robin Scheduler

and FIFO Selection

and Adaptive Shaper

(1 of 4)

Filler Cell

Idle Cell

to Cell_In_Control IDCR Generator

(1 of 4)

ICP Cell Group 1

ICP Cell Group 2

ICP Cell Group 3

Transmitter

Reference

Link Timing

ICP Cell Group 4

ICP Cell Buffer RAM

Next ICP Cell Group 1

ICP Cell Handler

Next ICP Cell Group 2

Next ICP Cell Group 3

Next ICP Cell Group 4

Note 1: This FIFO is the

TX UTOPIA FIFO when

the link is configured in

UNI Mode and it is the

TX LINK FIFO when it is

configured in IMA Mode.

Link 3

Figure 3 - Functional Block Diagram -Transmitter in IMA Mode

Section 5 describes the UTOPIA Interface in more

detail.

2.2 The ATM Transmission Convergence

The Transmit Convergence (TC) function is common

for both the IMA and UNI modes. It integrates the

circuitry to support ATM cell payload scrambling,

HEC generation and the generation of Idle/Filler/ICP

cells for use with the T1 and/or E1 trunks. Each of

the four MT90221 ATM TC circuits can use the

polynomial X43 + 1 to scramble the ATM cell payload

field. The MT90221 ATM cell payload scrambling

function can be disabled.

The ITU I.432 polynomial X8 + X2 + X + 1 is used to

generate the HEC field of the ATM cell. By default,

the ATM Forum polynomial X6 + X4 + X2 + 1 is added

to the calculated HEC octet. The addition of the ATM

Forum polynomial can be disabled.

The resulting calculation is then over-written on the

HEC field and the ATM cell is ready (i.e., complies

with the IMA transmit protocol) for transmission over

the PCM Interface.

In cases where the TC block requests a cell to be

transferred to any of the PCM Interfaces and the TX

UTOPIA FIFO has no cell ready for transmission,

then the TC block will automatically send an IDLE

cell (in UNI) or a Filler cell (in IMA mode) to the line.

The default values for the Idle and the Filler cells

comply with the ATM IMA Specification and are pre-

loaded in the MT90221 following a reset. The TX

Cell RAM Control register can be used to re-

initialize the TX Cell RAM.

2.2.1 TX Cell Ram and TX FIFO Length

The internal TX Cell Ram can hold up to 64 cells.

The following six cells are reserved for MT90221

operation:

• one ICP cell for each IMA Group for a total of

four cells

10

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