XRT73L03IV datasheet(29/62 Pages) EXAR

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3 CHANNEL E3/DS3/STS-1 LINE INTERFACE UNIT

XRT73L03

PRELIMINARY

REV. P1.0.13

b. Operating in the HOST Mode.

To configure the Data Rate of a Channel, write the

appropriate values into the STS-1/DS3_Ch(n) and

E3_Ch(n) bit-fields in Command Register CR4-(n).

NOTE: Reference Table 2 for the correct address of each

channel.

Table 4 relates the values of these two bit-fields to the

selected data rates.

2.0

THE TRANSMIT SECTION

Figure 8 shows the Transmit Section in each Channel

of the XRT73L03 consists of the following blocks:

• Transmit Logic Block

• TxClk(n) Duty Cycle Adjust Block

• HDB3/(B3ZS) Encoder

• Pulse Shaping Block

The purpose of the Transmit Section in each Channel

of the XRT73L03 is to take TTL/CMOS level data

from the Terminal Equipment and encode it into a for-

mat that can:

1. be efficiently transmitted over coaxial cable at E3,

DS3 or STS-1 data rates,

2. be reliably received by the Remote Terminal

Equipment at the other end of the E3, DS3 or

STS-1 data link, and

3. comply with the applicable pulse template

requirements.

The circuitry that the Transmit Section in each Chan-

nel of the XRT73L03 takes to accomplish this goal is

discussed below.

2.1

THE TRANSMIT LOGIC BLOCK

The purpose of the Transmit Logic Block is to accept

either Dual-Rail or Single-Rail (binary data stream)

TTL/CMOS level data and timing information from the

Terminal Equipment.

2.1.1

Accepting Dual-Rail Data from the Termi-

nal Equipment

Whenever the XRT73L03 accepts Dual-Rail data

from the Terminal Equipment, it does so via the fol-

lowing input signals:

• TPData(n)

• TNData(n)

• TxClk(n)

Figure 9 illustrates the typical interface for the trans-

mission of data in a Dual-Rail Format between the

Terminal Equipment and the Transmit Section of the

XRT73L03.

TABLE 3: SELECTING THE DATA RATE FOR CHANNEL(N) OF THE XRT73L03, VIA THE E3_CH(N) AND STS-1/

DS3_CH(N) INPUT PINS (HARDWARE MODE)

DATA RATE

STATE OF E3_CH(N) PIN

(PIN 64, 92, 102)

STATE OF STS-1/DS3_CH(N)

(PIN 65, 95, 101)

MODE OF B3ZS/HDB3 ENCODER/

DECODER BLOCKS

E3 (34.368 Mbps)

X (Don't Care)

HDB3

DS3 (44.736 Mbps)

B3ZS

STS-1 (51.84 Mbps)

B3ZS

COMMAND REGISTER CR4-(N)

STS-1/(DS3)_(n))

E3_Ch(n)

LLB(n) RLB(n)

TABLE 4: SELECTING THE DATA RATE FOR CHANNEL(N)

OF THE

XRT73L03 VIA THE STS-1/DS3_CH(N) AND

THE

E3_CH(N) BIT-FIELDS IN THE APPROPRIATE

COMMAND REGISTER (HOST MODE)

SELECTED DATA

RATE

STS-1/DS3_(N)

(D3)

E3_CH(N)

(D2)

X (Don't Care)

DS3

STS-1

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