XRT72L13 datasheet(46/370 Pages) EXAR

46 / 370 page

XRT72L13

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M13 MULTIPLEXER/CLEAR CHANNEL DS3 FRAMER IC

REV. P1.0.6

PRELIMINARY

190

RxPOS

Receive Positive Data Input:

The exact role of this input pin depends upon whether the Framer is

operating in the Unipolar or Bipolar Mode.

Unipolar Mode:

This input pin functions as the "Single-Rail" input for the "incoming"

DS3 data stream. The signal at this input pin will be sampled and

latched (into the Receive Framer block) on the "user-selected" edge

of the RxLineClk signal.

Bipolar Mode:

This input functions as one of the dual rail inputs for the incoming

AMI/B3ZS encoded DS3 data that has been received from an exter-

nal Line Interface Unit (LIU) IC. RxNEG functions as the other dual

rail input for the Framer. When this input pin is asserted, it means that

the LIU has received a "positive polarity" pulse from the line.

191

RxNEG

Receive Negative Data Input:

The exact role of this input pin depends upon whether the Framer is

operating in the Unipolar or Bipolar Mode.

Unipolar Mode:

This input pin is inactive, and should be pulled ("low" or "high") when

the Framer is operating in the Unipolar Mode.

Bipolar Mode:

This input pin functions as one of the dual rail inputs for the incoming

AMI/B3ZS encoded DS3 data that has been received from an exter-

nal Line Interface Unit (LIU) IC. RxPOS functions as the other dual

rail input for the Framer. When this input pin is asserted, it means that

the LIU has received a "negative polarity" pulse from the line.

192

RxOH

Receive Overhead Output Port:

All overhead bits, which are received via the "Receive Section" of the

Framer IC; will be output via this output pin, upon the rising edge of

RxOHClk.

193

RxOHEnable

Receive Overhead Enable Indicator:

The XRT72L13 will assert this output signal for one “RxOutClk” period

when it is safe for the Terminal Equipment to sample the data on the

“RxOH” output pin.

194

RxOHClk

Receive Overhead Clock:

The XRT72L13 will output the Overhead bits (within the incoming DS3

frames), via the "RxOH" output pin, upon the falling edge of this clock

signal.

As a consequence, the "user's data link equipment" should use the

rising edge of this clock signal to sample the data on both the "RxOH"

and "RxOHFrame" output pins.

NOTE: This clock signal is always active.

195

RxOHFrame

Receive Overhead Frame Boundary Indicator:

This output pin pulses "high" whenever the Receive Overhead Data

Output Interface outputs the first overhead bit (or nibble) of a new DS3

frame.

196

RxLOS

Receive Section - Loss of Signal Output Indicator:

This pin is asserted when the Receive Section encounters a string of

180 consecutive 0's via the RxPOS and RxNEG pins.

This pin will be negated once the Receive Section has detected at

least 60 pulses within 180 bit-periods.

PIN DESCRIPTIONS

PIN #NAME

TYPE

DESCRIPTION

XRT72L13 Datasheet(PDF) 46 Page - Exar Corporation

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