MT9174AE datasheet(5/22 Pages) MITEL

5 / 22 page

Preliminary Information

MT9173/74

9-141

Functional Description

The MT9173 and MT9174 are multifunction devices

capable of providing high speed, full duplex digital

transmission at up to 160 kbit/s over a twisted wire

pair. They use adaptive echo-cancelling techniques

and transfer data in a format compatible to the ISDN

basic rate. Several modes of operation allow an easy

interface

digital

telecommunication

networks

including

PCS

wireless

base

stations,

smart

telephone sets, workstations, data terminals and

computers. The device supports the 2B+D channel

format (two 64 kbit/s B-channels and one 16 kbit/s D-

channel) over two wires as recommended by the

CCITT. The line data is converted to and from the

ST-BUS format on the system side of the network to

allow for easy interfacing with other components

such

the

S-interface

device

NT1

arrangement, or to digital PABX components.

Smart telephone sets with data and voice capability

can be easily implemented using the MT9173/74 as

a line interface.

The device’s high bandwidth and

long loop length capability allows its use in a wide

variety of sets.

This can be extended to provide full

data and voice capability to the private subscriber by

the installation of equipment in both the home and

central ofﬁce or remote concentration equipment.

Within the subscriber equipment the MT9173/74

would terminate the line and encode/ decode the

data and voice for transmission while additional

electronics could provide interfaces for a standard

telephone set and any number of data ports

supporting standard data rates for such things as

computer communications and telemetry for remote

meter reading. Digital workstations with a high

degree of networking capability can be designed

using the DNIC for the line interface, offering up to

160 kbit/s data transmission over existing telephone

lines. The MT9173/74 could also be valuable within

existing computer networks for connecting a large

number

terminals

computer

for

intercomputer links. With the DNIC, this can be

accomplished at up to 160 kbit/s at a very low cost

per line for terminal to computer links and in many

cases

this

bandwidth

would

sufﬁcient

for

computer to computer links.

Figure 1 shows the block diagram of the MT9173/74.

The DNIC provides a bidirectional interface between

the DV (data/voice) port and a full duplex line

operating at 80 or 160 kbit/s over a single pair of

twisted wires. The DNIC has three serial ports. The

DV port (DSTi/Di, DSTo/Do), the CD (control/data)

port (CDSTi/CDi, CDSTo/CDo) and a line port (LIN,

LOUT). The data on the line is made up of information

from the DV and CD ports. The DNIC must combine

information received from both the DV and CD ports

and put it onto the line. At the same time, the data

received from the line must be split into the various

channels and directed to the proper ports. The

usable data rates are 72 and 144 kbit/s as required

for the basic rate interface in ISDN. Full duplex

transmission is made possible through on board

adaptive echo cancellation.

The DNIC has various modes of operation which are

selected through the mode select pins MS0-2. The

two major modes of operation are the MODEM

(MOD) and DIGITAL NETWORK (DN) modes. MOD

mode is a transparent 80 or 160 kbit/s modem.

DN mode the line carries the B and D channels

formatted for the ISDN at either 80 or 160 kbit/s. In

the DN mode the DV and CD ports are standard ST-

BUS and in MOD mode they are transparent serial

data streams at 80 or 160 kbit/s. Other modes

include: MASTER (MAS) or SLAVE (SLV) mode,

where the timebase and frame synchronization are

provided externally or are extracted from the line and

DUAL or SINGLE (SINGL) port modes, where both

the DV and CD ports are active or where the CD port

is inactive and all information is passed through the

DV port. For a detailed description of the modes see

“Operating Modes” section.

In DIGITAL NETWORK (DN) mode there are three

channels transferred by the DV and CD ports. They

are the B, C and D channels. The B1 and B2

channels each have a bandwidth of 64 kbit/s and are

used for carrying PCM encoded voice or data. These

channels

are

always

transmitted

and

received

through the DV port (Figures 3, 4, 5, 6). The C-

channel, having a bandwidth of 64 kbit/s, provides a

means for the system to control the DNIC and for the

DNIC to pass status information back to the system.

The C-channel has a Housekeeping (HK) bit which is

the only bit of the C-channel transmitted and

received on the line. The 2B+D channel bits and the

HK bit are double-buffered. The D-channel can be

transmitted or received on the line with either an 8,

16 or 64 kbit/s bandwidth depending on the DNIC’s

mode of operation. Both the HK bit and the D-

channel can be used for end-to-end signalling or low

speed data transfer. In DUAL port mode the C and D

channels are accessed via the CD port (Figure 7)

while in SINGL port mode they are transferred

through the DV port (Figures 5, 6) along with the B1

and B2 channels.

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