XRT7250 datasheet(32/463 Pages) EXAR

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DS3/E3 FRAMER IC

XRT7250

REV. 1.1.1

RxLineClk

Receiver LIU (Recovered) Clock:

This input signal serves three purposes:

1. The Receive Framer uses it to sample and "latch" the signals at the RxPOS

and RxNEG input pins (into the Receive Framer circuitry).

2. This input signal functions as the timing reference for the Receive Framer

block.

3. The Transmit Framer block can be configured to use this input signal as its

timing reference.

This signal is the recovered clock from the external DS3/E3 LIU (Line Interface

Unit) IC, which is derived from the incoming DS3/E3 data.

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/

HDB3 encoded DS3 or E3 data that has been received from an external 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.

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" E3 data

stream. The signal at this input pin will be sampled and latched (into the

Receive DS3/E3 Framer) 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/HDB3

encoded DS3 or E3 data that has been received from an external Line Inter-

face 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.

RLOL

Receive Loss of Lock Indicator - from the XRT7300 DS3/E3 Line

Interface Unit IC.

This input pin is intended to be connected to the RLOL (Receive Loss of Lock)

output pin of the XRT7300 Line Interface Unit IC. The user can monitor the

state of this pin by reading the state of Bit 1 (RLOL) within the Line Interface

Scan Register (Address = 0x81).

If this input pin is "low", then it means that the "clock recovery phase-locked-

loop" circuitry, within the XRT7300 device is properly locked onto the incoming

DS3 E3 data-stream; and is properly recovering clock and data from this DS3/

E3 data-stream. However, if this input pin is "high", then it means that the

phase-locked-loop circuitry, within the XRT7300 device has lost lock with the

incoming DS3 or E3 data-stream, and is not properly recovering clock and

data.

For more information on the operation of the XRT7300 DS3/E3 Line Interface

Unit IC, please consult the "XRT7300 DS3/E3 Line Interface Unit" data sheet.

If the customer is not using the XRT7300 DS3/E3 Line Interface Unit IC, he/she

can use this input pin for other purposes.

PIN DESCRIPTION

PIN #NAME

TYPE

DESCRIPTION

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