XRT72L53 Datasheet, PDF (17/467 Pages) Exar Corporation – THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER

XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
REV. P1.1.7
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PRELIMINARY
PIN DESCRIPTION CONNECTED PINS
PIN #
D20
PIN NAME
RxClk[0]
E1
TxFrameRef[0]
E2
TxLineClk[0]
TYPE
O
I
O
DESCRIPTION
Receive Clock Output Signal for Serial and Nibble/Parallel Data
Interface - Channel 0:
The exact behavior of this signal depends upon whether the XRT72L53
is operating in the Serial or in the Nibble-Parallel-Mode.
Serial Mode Operation:
In the serial mode, this signal is a 44.736MHz clock output signal (for
DS3 applications) or 34.368MHz clock output signal (for E3 applica-
tions). The Receive Payload Data Output Interface will update the data
via the RxSer[0] output pin, upon the rising edge of this clock signal.
The user is advised to design (or configure) the Terminal Equipment to
sample the data on the RxSer[0] pin, upon the falling edge of this clock
signal.
Nibble-Parallel Mode Operation:
In this Nibble-Parallel Mode, Channel 0 will derive this clock signal, from
the RxLineClk[0] signal. Channel 0 will pulse this clock signal 1176
times for each inbound DS3 frame (or 1074 times for each inbound “E3/
ITU-T G.832” frame, or 384 times for each inbound “E3/ITU-T G.751
frame). The Receive Payload Data Output Interface will update the data,
on the RxNib[3:0][0] output pins upon the falling edge of this clock sig-
nal.
The user is advised to design (or configure) the Terminal Equipment to
sample the data on the RxNib[3:0][0] output pins, upon the rising edge
of this clock signal
Transmit Framer Reference Input - Channel 0:
This input pin functions as the Transmit Frame Generation reference
signal, if Channel 0 has been configured to operate in the Local-Time/
Frame Slave Mode. If Channel 0 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 microsec-
onds (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 Channel
0 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 XRT72L53 Framer IC to operate in
the Local Time/Frame Slave Mode by writing "xxxx xx01" into the
Framer Operating Mode Register (Address = 0x00).
Transmit Line Interface Clock output - Channel 0:
This clock signal is output to the Line Interface Framer, along with the
TxPOS[0] and TxNEG[0] signals. The purpose of this output clock sig-
nal is to provide the LIU with timing information that it can use to gener-
ate the AMI pulses and deliver them over the transmission medium to
the Remote Terminal Equipment. The user can configure the source of
this clock to be either the RxLineClk[0] (from the Receiver portion of
Channel 0) or the TxInClk[0] input. The nominal frequency of this clock
signal is 34.368 MHz (for E3 applications), or 44.736MHz for DS3 appli-
cations.
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