XRT7245
DS3 UNI FOR ATM
á
PRELIMINARY
REV. 1.03
20
102
StuffCtl
I
External PLCP Frame Stuff Control:
This input allows the user to externally exercise
or forego trailer nibble stuffing opportunities by the Transmit PLCP Processor. PLCP
trailer nibble stuff opportunities occur in periods of three PLCP frames (375μs). The
first PLCP frame (first within a “stuff opportunity” period) will have 13 trailer nibbles
appended to it. The second PLCP frame (second within a “stuff opportunity” period)
will have 14 trailer nibbles appended to it. The third PLCP frame (the location of the
stuff opportunity) will contain 13 trailer nibbles if the StuffCtl input is “l(fā)ow” and 14 trailer
nibbles is the StuffCtl input is “high”.
103
TxInClk
I
Transmit DS3 Framer—Clock Signal:
The Transmit DS3 Framer can be configured
to use this input signal as the timing reference. If this input pin is chosen to be the tim-
ing reference, then the user must supply a high quality 44.736 MHz signal to this input
pin. In this configuration, frame generation, by the Transmit DS3 Framer, will be asyn-
chronous (with any other timing signals within the UNI). However, frame timing will be
based upon this clock signal.
Note:
This input pin should be tied to “GND” if it is not used as the Transmit DS3
Framer timing reference.
104
RxPLOF
O
Receive PLCP—“Loss of Frame” Output Indicator:
The Receive PLCP Processor
will assert this pin, when it declares a “Loss of Frame” condition. This output will be
negated when the Receive PLCP Processor reaches the “In Frame” Condition.
105
GND
***
Ground Signal Pin
106
RxPOOF
O
Receive PLCP “Out of Frame” Indicator:
The Receive PLCP Processor will assert
this pin, when it declares an “Out of Frame” condition. This output will be negated
when the Receive PLCP Processor reaches the “In Frame” Condition.
107
TxFrameRef
I
Transmit DS3 Framer—Frame Reference Input Pin:
The Transmit DS3 Framer can
be configured to use this input signal as the “framing” reference for the Transmit DS3
Framer block. If this input pin is chosen to be the timing reference, then any rising
edge at this input will cause the Transmit DS3 Framer to begin its creation a new DS3
M-frame. Consequently, the user must supply a clock signal that is equivalent to the
DS3 Frame rate (or 9398.3 Hz).
Note:
This input pin should be tied to “GND” if it is not used as the Transmit DS3
Framer frame reference signal.
108
TxPFrame
O
Transmit PLCP Frame Boundary Indicator—Output:
This output pin pulses “high”
once for each outbound PLCP frame, when the last nibble is being routed to the Trans-
mit DS3 Framer.
109
TxPOS
O
Transmit Positive Polarity Pulse:
The exact role of this output pin depends upon
whether the UNI is operating in the Unipolar or Bipolar Mode.
Unipolar Mode:
This output pin functions as the “Single-Rail” output signal for the “out-
bound” DS3 data stream. The signal, at this output pin, will be updated on the “user-
selected” edge of the TxLineClk signal.
Bipolar Mode:
This output pin functions as one of the two dual rail output signals that
commands the sequence of pulses to be driven on the line. TxNEG is the other output
pin. This input is typically connected to the TPDATA input of the external DS3 Line
Interface Unit IC. When this output is asserted, it will command the LIU to generate a
positive polarity pulse on the line.
110
TxPO-
HFrame
O
Transmit PLCP Frame Path Overhead Byte Serial Input Port—Beginning of
Frame indicator.
This output pin, along with the TxPOH, TxPOHClk, and TxPOHIns
pins comprise the “Transmit PLCP Frame POH Byte Insertion” serial input port. This
particular pin will pulse “high” when the “Transmit PLCP POH Byte Insertion” serial
input port is expecting the first bit of the Z6 byte at the TxPOH input pin.
PIN DESCRIPTION (CONT’D)
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IN
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YMBOL
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ESCRIPTION