XRT7250 Datasheet, PDF (32/463 Pages) Exar Corporation – DS3/E3 FRAMER IC

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PIN DESCRIPTION
PIN #
74
NAME
RxLineClk
75
RxNEG
76
RxPOS
77
RLOL
DS3/E3 FRAMER IC
XRT7250
REV. 1.1.1
TYPE
DESCRIPTION
i 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.
I 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.
I 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.
I 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.
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