XRT73LC04A
4 CHANNEL DS3/E3/STS-1 LINE INTERFACE UNIT
REV. 1.0.1
RPOS_(n) and RNEG_(n) output pins on the rising
edge of RxClk_(n).
F
IGURE
29. H
OW THE
XRT73LC04A
OUTPUTS DATA ON THE
RPOS
AND
RNEG
OUTPUT PINS
RPOS
RNEG
RxClk
RxClk_(n) is the Recovered Clock signal from the in-
coming Received line signal. As a result, these clock
signals are typically 34.368 MHz for E3 applications,
44.736 MHz for DS3 applications and 51.84 MHz for
SONET STS-1 applications.
In general, if a given channel received a positive-po-
larity pulse in the incoming line signal via the
RTIP_(n) and RRing_(n) input pins, then the channel
pulses its corresponding RPOS_(n) output pin “High".
Conversely, if the channel received a negative-polari-
ty pulse in the incoming line signal via the RTIP_(n)
and RRing_(n) input pins, then the channel(n) pulses
its corresponding RNEG_(n) output pin “High".
Inverting the RxClk_(n) outputs
Each channel can invert the RxClk_(n) signals with
respect to the delivery of the RPOS_(n) and
RNEG_(n) output data to the Receiving Terminal
Equipment. This feature may be useful for those cus-
tomers whose Receiving Terminal Equipment logic
design is such that the RPOS_(n) and RNEG_(n) da-
ta must be sampled on the rising edge of RxClk_(n).
RNEG_(n) and RxClk_(n) signals when the
RxClk_(n) signal has been inverted.
In the Hardware Mode:
Setting the RxClkINV pin “High” results in all chan-
nels of the XRT73LC04A to output the recovered da-
ta on RPOS_(n) and RNEG_(n) on the falling edge of
RxClk_(n). Setting this pin “Low” results in the recov-
ered data on RPOS_(n) and RNEG_(n) to output on
the rising edge of RxClk_(n).
F
IGURE
30. T
HE
B
EHAVIOR OF THE
RPOS, RNEG,
AND
R
X
C
LK SIGNALS WHEN
R
X
C
LK IS INVERTED
RPOS
RNEG
RxClk
a. Operating in the HOST Mode
In order to configure a channel(n) to invert the
RxClk_(n) output signal, the XRT73LC04A must be
operating in the HOST Mode.
To invert RxClk_(n), associated with Channel(n),
write a "1" into the RxClk_(n)INV bit-field within Com-
mand Register CR-3.
44
EXAR [ EXAR CORPORATION ]
