XRT75R12DIB datasheet(39/133 Pages) EXAR

39 / 133 page

XRT75R12D

REV. 1.0.3

TWELVE CHANNEL E3/DS3/STS-1 LINE INTERFACE UNIT WITH SONET DESYNCHRONIZER

6.0

THE TRANSMITTER SECTION

The transmitter is designed so that the LIU can accept serial data from a local device, encode the data

properly, and then output an analog pulse according to the pulse shape chosen in the appropriate registers.

This section describes the detailed operation of various blocks within the transmit path. A simplified block

diagram of the transmit path is shown in Figure 22.

Transmit Digital Input Interface

The method for applying data to the transmit inputs of the LIU is a serial interface consisting of TxClk, TxPOS,

and TxNEG. For single rail mode, only TxClk and TxPOS are necessary for providing the local data from a

Framer device or ASIC. Data can be sampled on either edge of the input clock signal by programming the

appropriate register. A typical interface is shown in Figure 23.

FIGURE 22. TRANSMIT PATH BLOCK DIAGRAM

FIGURE 23. TYPICAL INTERFACE BETWEEN TERMINAL EQUIPMENT AND THE XRT75R12D (DUAL-RAIL DATA)

Channel n

Device

Monitor

MTIP_n

MRing_n

DMO_n

Timing

Control

Pulse

Shaping

HDB3/

B3ZS

Encoder

Control

Jitter

Attenuator

MUX

Line

Driver

TxON

TxClk_n

TxPOS_n

TxNEG_n

TTIP_n

TRing_n

Terminal

Equipment

(E3/DS3 or STS-1

Framer)

Exar E3/DS3/STS-1 LIU

Transmit

Logic

Block

TxPOS

TxNEG

TxLineClk

TPData

TNData

TxClk

XRT75R12DIB Datasheet(PDF) 39 Page - Exar Corporation

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