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MC145574

ISDN S/T-Interface Transceiver

Motorola => Freescale 

Freescale Semiconductor, Inc.

2

WIRING CONFIGURATIONS

2.1

INTRODUCTION

The MC145574 ISDN S/T transceiver conforms to CCITT I.430, ETSI ETS 300012, and ANSI T1.605

specifications. It is a layer 1 transceiver designed for use at the ISDN S and T reference points. It

is designed for both point–to–point and multipoint operation. The S/T transceiver is designed for use

in either the network terminating (NT) mode or in the terminal endpoint (TE) applications. Two 64 kpbs

B channels and one 16 kbps D channel are transmitted in a full–duplex fashion across the interface.

Sections 2.2 through 2.6 contain suggested wiring configurations for use. These configurations are

deemed to be the most common but by no means the only wiring configurations. Section 16 specifies

the recommended circuitry for interfacing the MC145574 to the S/T bus. Note that when operating

in the TE mode, only one TE has the 100 Ω termination resistors in the transmit and receive paths.

Figures 2–1 through 2–4 illustrate where to connect the termination resistors for the described loop

configurations.

A description of the most commonly used loop configurations is as described below.

2.2

POINT-TO-POINT OPERATION

In the point–to–point mode of operation, one NT communicates with one TE. As such, 100 Ω termina-

tion resistors must be connected across the transmit and receive paths of both the NT and TE transceiv-

ers. Figure 2–1 illustrates this wiring configuration.

When using the MC145574 in this configuration, the NT must be in adaptive timing. This is accom-

plished by holding the FIX pin low; i.e., connecting it to VSS. Refer to Section 6 for a more detailed

description of this pin function. CCITT I.430, ETSI ETS 300012, and ANSI T1.605 specify that the

S/T transceiver must be able to operate up to a distance of 1 km in the point–to–point mode. This

is the distance D1 as shown in Figure 2–1.

NT

<

D1

>

TE

TxP

TR

TxN

MC145574

RxP

TR

RxN

RxP

TR

RxN

MC145574

TxP

TR

TxN

Figure 2–1. Point–to–Point

MOTOROLA

For More InforMmCa1t4io55n7O4 n This Product,

2–1

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