XRT73LC00A_08 Datasheet, PDF (12/63 Pages) Exar Corporation – E3/DS3/STS-1 LINE INTERFACE UNIT

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PIN DESCRIPTION
PIN #
22
SYMBOL
CS/(DR/SR)
23
RLOL
24
RLOS
25
DGND
26
DVDD
27
EXCLK
28
RxDGND
29
RxDVDD
XRT73LC00A
E3/DS3/STS-1 LINE INTERFACE UNIT
TYPE
I
DESCRIPTION
Microprocessor Serial Interface - Chip Select/Encoder and Decoder Disable
The function of this input pin depends upon whether the XRT73LC00A is operat-
ing in the HOST or the Hardware Mode.
HOST Mode - Chip Select Input:
The Local Microprocessor must assert this pin (e.g., set it to “0”) in order to
enable communication with the XRT73LC00A via the Microprocessor Serial
Interface.
Hardware Mode - Dual-Rail/Single-Rail Select Input:
Setting this input pin “High” configures the XRT73LC00A to operate in the Dual-
Rail Mode. When the XRT73LC00A is operating in this mode, then the Receive
Section of the LIU IC outputs the Recovered Data via both RPOS and RNEG
output pins.
Setting this input pin “Low” configures the XRT73LC00AXRT73LC00A to oper-
ate in the Single-Rail Mode. When the XRT73LC00A is operating in this mode,
the Receive Section of the LIU IC outputs the Recovered Data via the RPOS
output pin in a binary data stream. No data will output via the RNEG output pin.
O Receive Loss of Lock Output Indicator
This output pin toggles “High” if the XRT73LC00A has detected a Loss of Lock
Condition. The XRT73LC00A declares an LOL (Loss of Lock) Condition if the
recovered clock frequency deviates from the Reference Clock frequency (avail-
able at the EXCLK input pin) by more than 0.5%.
NOTE: The RCLK1/2 output pins are sourced by the signal applied at the EXCLK
input pin anytime the XRT73LC00A declares an LOL condition.
O Receive Loss of Signal Output Indicator
This output pin toggles “High” if the XRT73LC00A has detected a Loss of Signal
Condition in the incoming line signal.
The criteria the XRT73LC00A uses to declare an LOS Condition depends upon
whether the device is operating in the E3 or DS3/STS-1 Mode.
**** Digital Ground
**** Digital Power Supply
I
External Reference Clock Input:
Apply a line-rate clock signal to this input pin. This signal is a 34.368MHz clock
signal for E3 applications, a 44.736 MHz clock signal for DS3 applications or a
51.84 MHz clock signal for SONET STS-1 applications.
NOTE: This input pin functions as the source of the RxCLK output clock signal
any time the XRT73LC00A declares an LOL condition.
**** Receiver Digital Ground
**** Receiver Digital Power Supply
7