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MC145474

ISDN S/T Interface Transceiver

Motorola => Freescale 

SECTION 3

ACTIVATION/DEACTIVATION OF S/T TRANSCEIVER

3.1 INTRODUCTION

CCITT I.430 and ANSI T1.605 define five information states for the S/T transceiver. When the NT

is in the fully operational state it transmits INFO 4. When the TE is in the fully operational state it

transmits INFO 3. INFO 1 is transmitted by the TE when it wants to wake up the NT. INFO 2 is

transmitted by the NT when it wants to wake up the TE, or in response to the TEs transmitted INFO

1. These states cause unique patterns of symbols to be transmitted over the S/T interface. Only

when the S/T loop is in the fully activated state are the 2B+D channels of data transmitted over the

interface.

3.2 TRANSMISSION STATES FOR NT MODE S/T TRANSCEIVER

When configured as an NT, an S/T transceiver can be in any of the following transmission states

shown in Table 3-1.

Table 3-1. NT Mode Transmission States

Information State

INFO 0

INFO 2

INFO 4

Description

The NT transmits 1s in every bit position. This corresponds to no signal

being transmitted.

The NT sets its B1, B2, D, and E channels to ‘0’. The A bit is set to ‘0’ (see

Sections 3.11.1 and 3.11.2).

INFO 4 corresponds to frames containing operational data on the B1, B2,

D, and E channels. The A bit is set to ‘1’.

3.3 TRANSMISSION STATES FOR TE MODE S/T TRANSCEIVER

When configured as a TE, an S/T transceiver can be in any of the following transmission states

shown in Table 3-2.

Table 3-2. TE Mode Transmission States

Information State

INFO 0

INFO 1

INFO 3

Description

The TE transmits 1s in every bit position. This corresponds to no signal

being transmitted.

The TE transmits a continuous signal with the following pattern: positive

zero, negative zero, six ones. This signal is asynchronous to the NT.

INFO 3 corresponds to frames containing operational data on the B1, B2,

and D channels. If INFO 4 or INFO 2 is being received, INFO 3 will be

synchronised to it.

3.4 ACTIVATION OF S/T LOOP BY NT

The NT activates the loop by transmitting INFO 2 to the TE or TEs. This is accomplished in the

MC145474/75 by setting NR2(3) to a ‘1’ (see Section 3.11.3). Note that this bit is internally reset

to ‘0’ after the internal activation state machine has recognized its active transition.

MC145474 • MC145475

MOTOROLA

3-1

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