XRT72L56 Datasheet, PDF (33/486 Pages) Exar Corporation – SIX CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER

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PRELIMINARY
XRT72L56
SIX CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
REV. P1.1.2
PIN DESCRIPTION FOR THE XRT72L56
PIN #
G1
G2
G3
G4
G23
G24
G25
G26
H1
PIN NAME
RxNEG[0]
RLOL[2]
EncoDis[2]
TxLev[2]
TxOHFrame[2]/
TxHDLCClk[2]
TxOHIns[2]/
TxHDLCDat4[2]
TxNib1[2]/
TxHDLCDat1[2]
TxNib3[2]/
TxHDLCDat3[2]
TxFrameRef[0]
TYPE
I
I
O
O
O
DESCRIPTION
Receive Negative 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 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.
See Description for Pin B3
See Description for Pin B4
See Description for Pin B5
See Description for Pin B13
I
See Description for Pin A16
I
See Description for Pin D14
I
See Description for Pin B15
I
Transmit Framer Reference Input:
This input pin functions as the "Transmit Frame Generation" reference sig-
nal, if the XRT72l56 device has been configured to operate in the "Local-
Time/Frame Slave" Mode. If the XRT72l56 device has been configured to
operate in the "Local-Time/Frame-Slave" Mode, then the user's terminal
equipment is expected to apply a pulse (to this input pin) once every 106.4
microseconds (for DS3 applications); once every 125 microseconds (for E3,
ITU-T G.832 applications) or once every 44.7 microseconds (for E3, ITU-T
G.751 applications).
In the "Local-Time/Frame-Slave" Mode, the Transmit Section of the
XRT72l56 Framer IC will initiate its generation of a new "outbound" DS3 or
E3 frame, upon the rising edge of this signal.
NOTE: The user can configure the XRT72l56 Framer IC to operate in the
"Local Time/Frame Slave" Mode by writing "xxxx xx01" into the "Framer
Operating Mode" Register (Address = 0x00).
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