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PRELIMINARY
DS3 UNI FOR ATM
XRT7245
REV. 1.03
19
95
RxOHFrame
O
Receive DS3 Framer Overhead Bit Serial Output Port—Frame Boundary Indica-
tor:
This pin, along with the RxOH and RxOHClk signals comprise the “Receive DS3
Framer OH Bit” Serial Output Port. This pin pulses high when the first overhead bit of
a DS3 frame (e.g., the X-bit in F-Frame 1) is output at the RxOH pin.
96
RxFrame
O
Receive Boundary of DS3 Frame Output Indicator:
This output pin indicates the
boundary of the incoming DS3 frame as they appear, at the RxPOS and RxNEG
inputs. This pin marks the end of a DS3 frame by pulsing high for one bit period at the
end of each frame.
97
RxPOS
I
Receive Positive Data Input:
The exact role of this input pin depends upon whether
the UNI 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 DS3 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/
B3ZS encoded DS3 data that has been received from an external Line Interface Unit
(LIU) IC. RxNEG functions as the other dual rail input for the UNI. When this input pin
is asserted, it means that the LIU has received a “positive polarity” pulse from the line.
98
RxNEG
I
Receive Negative Data Input:
The exact role of this input pin depends upon whether
the UNI is operating in the Unipolar or Bipolar Mode.
Unipolar Mode:
This input pin is inactive, and should be pulled (“l(fā)ow” or “high”) when
the UNI 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 external Line Interface
Unit (LIU) IC. RxPOS functions as the other dual rail input for the UNI. When this input
pin is asserted, it means that the LIU has received a “negative polarity” pulse from the
line.
99
RxLineClk
I
Receiver LIU (Recovered) Clock:
This input signal serves three purposes:
1. The Receive DS3 Framer uses it to sample and “l(fā)atch” the signals at the RxPOS
and RxNEG input pins (into the Receive DS3 Framer circuitry).
2. This input signal functions as the timing reference for the Receive Framer block.
3. The Transmit DS3 Framer block can be configured to use this input signal as its tim-
ing reference.
Note:
This signal is the recovered clock from the external DS3 LIU (Line Interface
Unit) IC, which is derived from the incoming DS3 data.
100
RxPRed
O
Receiver Red Alarm Indicator—Receive PLCP Processor:
The UNI asserts this
output pin to denote that one of the following events has been detected by the Receive
PLCP Processor:
OOF—Out of Frame Condition
LOF—Loss of Frame Condition
101
RxRed
O
Receiver Red Alarm Indicator—Receive DS3 Framer:
The UNI asserts this output
pin to denote that one of the following events has been detected by the Receive DS3
Framer:
LOS—Loss of Signal Condition
OOF—Out of Frame Condition
AIS—Alarm Indication Signal Detection
PIN DESCRIPTION (CONT’D)
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ESCRIPTION