XRT72L56 Datasheet, PDF (34/486 Pages) Exar Corporation – SIX CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER

XRT72L56
SIX CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
REV. P1.1.2
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PRELIMINARY
PIN DESCRIPTION FOR THE XRT72L56
PIN #
H2
H3
H4
H23
H24
H25
H26
J1
PIN NAME
RxPOS[0]
TxInClk[0]
DMO[2]
TxNib0[2]/
TxHDLCDat0[2]
TxSer[2]/
SndMsg[2]
NC
NC
TxPOS[0]
TYPE
I
I
I
I
DESCRIPTION
Receive Positive Data Input:
The exact role of this input pin depends upon whether the Framer is operat-
ing 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 sig-
nal.
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 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.
Transmit Framer Reference Clock Input:
This input pin functions as the "Timing Reference" for the Transmit Section
of the XRT72l56 Framer IC; if the device has been configured to operate in
the "Local-Time" Mode. Further, if the XRT72l56 Framer IC has been con-
figured to operate in the "Local-Time" Mode, the "Transmit Payload Data
Input Interface will sample the data at the TxSer input pin, upon the rising
edge of "TxInClk".
For E3 applications, the user should apply a 34.368MHz clock signal. For
DS3 applications, the user should apply a 44.736MHz clock signal.
The user can configure the XRT72l56 Framer IC to operate in the "Local-
Time" mode by writing "xxxx xx01" or "xxxx xx1x" into the "Framer Operat-
ing Mode" register (Address = 0x00)
See Description for Pin D7
See Description for Pin A23
I
See Description for Pin A24
O Transmit Positive Polarity Pulse:
The exact role of this output pin depends upon whether the Framer is oper-
ating in the Unipolar or Bipolar Mode.
Unipolar Mode:
This output pin functions as the "Single-Rail" output signal for the "out-
bound" DS3 or E3 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 com-
mands 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 or E3 Line Interface Unit IC. When this output is asserted, it
will command the LIU to generate a positive polarity pulse on the line
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