MT90221 Просмотр технического описания (PDF) - Mitel Networks

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MT90221

Quad IMA/UNI PHY Device

Mitel Networks 

MT90221

1.0 Device Architecture

The MT90221, supported by software, implements

the ATM Forum Inverse Multiplexing for

Asynchronous Transfer Mode (IMA) Specification.

This approach minimizes the impact of any changes

that might occur in the specification. Actions are

implemented by the MT90221 and decisions by the

software.

The MT90221 supports the following two major

modes of operation:

• the IMA mode (as defined by the ATM Forum

IMA Specification)

• the User Network Interface (UNI) mode

Up to four IMA Groups can be implemented. Any of

the four PCM Interfaces can be assigned

dynamically to any of these IMA Groups. A different

UTOPIA PHY address is assigned to each of the IMA

Groups.

The UNI mode is used to transfer the cells from the

UTOPIA Interface to a PCM port without any

overhead. Up to 4 UTOPIA PHY addresses can be

supported in UNI mode.

The MT90221 also supports a mixed mode where

the PCM Interfaces not assigned to an IMA Group

can be used in UNI mode.

The IMA implementation is divided into hardware

and software functions. The MT90221 implements

the hardware functions. The software functions are

implemented by the user. The hardware and

software functions are described below. Notice that a

number of MT90221 functions are included to assist

in the collection of statistical information. This

information supports the MIB implementation.

1.1 Software Functions

For the MT90221 to comply with the IMA

specification, the following functions must be

implemented by software:

• the transmit and receive Link State Machines

(LSM)

• the IMA Group State Machines (GSM)

• the IMA Group Traffic State Machines (GTSM)

• the Operations and Maintenance (OAM)

functions

1.1.1 Link State Machines

The software implemented transmit and receive

LSMs are independent (i.e., each link has its own

LSM). LSMs rely on various events from the

MT90221 interface, such as cell errors, excessive

delay between-links, etc.; or, from the T1 or E1

framer, such as Loss Of Signal (LOS), Loss Of

Frame (LOF), Remote Alarm Indication (RAI) etc.

On-chip registers are used to generate the ICP cells

that communicate the LSM states to the Far End

(FE).

1.1.2 IMA Group State Machines

The IMA GSMs and Group Traffic State Machines

(GTSM) must be implemented in software. One of

each state machine should be implemented for each

IMA Group.

On-chip registers are used to generate the ICP cells

that communicate the various states to the FE.

1.1.3 Link Addition, Removal or Restoration

The addition, removal or restoration of a link is

controlled by software using the various control

registers in the MT90221 and in the T1 or E1

framers. Decisions are based on the MT90221 and

T1 or E1 framers status registers.

1.1.4 Interrupt

The MT90221 provides numerous registers and

counters to implement a polling and/or interrupt

mechanism for tracking link and IMA Group status.

This traffic in and out information is used by the

Management Information Base (MIB) for each IMA

Group.

1.1.5 Signaling and Rate Adjustment

The microprocessor controls the operation of the T1

or E1 link by providing handshaking between the FE

and Near Ends (NE) including such functions as

signaling and loopback controls. Rate adjustment is

controlled by:

• adding or removing one or more T1 or E1 links

• providing feedback to the ATM network for adjust-

ing the ATM traffic.

1.1.6 Performance Monitoring

Software implements most of the performance

monitoring. The MT90221 provides status

information for:

• the Cell Delineation Block and IMA Frame State

Machine

• the number of ICP violations

• the total number of cells

• the number of idle or discarded cells.

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