Connection Diagram

TLH11924 – 2

Top View

Order Number TP3404V

See NS Package Number V28A

Functional Description

The QDASL contains 4 transceivers each of which can in-

teroperate with any of the TP340X family of single-channel

DASL transceivers Each QDASL transceiver has its own

independent line transmit and receive section timing recov-

ery circuit scramblerdescrambler and loop activation con-

troller Functions which are shared by the 4 transceivers

include the Microwire control port and the digital interface

with time-slot assignment

BURST MODE OPERATION

For full-duplex operation over a single twisted-pair burst

mode timing is used with the QDASL end of each line act-

ing as the loop timing master and the DASL at the terminal

being the timing slave (the QDASL transceivers cannot op-

erate in loop timing slave mode)

Each burst within a DASL line is initiated by the QDASL

Master transmitting a startbit for burst framing followed by

the B1 B2 and D channel data from 2 consecutive 8 kHz

frames combined in the format shown in

Figure 1 During

transmit bursts the receiver input for that channel is inhibit-

ed to avoid disturbing the adaptive circuits The slave’s re-

ceiver is enabled at this time and it synchronizes to the start

bit of the burst which is always an unscrambled ‘‘1’’ (of the

opposite polarity to the last ‘‘1’’ sent in the previous burst)

When the slave detects that 36 bits following the start bit

have been received it disables the received input waits 6

line symbol periods to match the other end settling guard

time and then begins to transmit its burst back towards the

master which by this time has enabled its receiver input

The burst repetition rate is thus 4 KHz

LINE TRANSMIT SECTIONS

Alternate Mark Inversion (AMI) line coding in which binary

‘‘1’’s are alternately transmitted as a positive pulse then a

negative pulse is used on each DASL line because of its

spectral efficiency and null DC energy content All transmit-

ted bits excluding the start bit are scrambled by a 9-bit

scrambler to provide good spectral spreading with a strong

TLH11924 – 3

FIGURE 1 Burst Mode Timing on the Line

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