XRT75R03D datasheet(21/134 Pages) EXAR

21 / 134 page

XRT75R03D

THREE CHANNEL E3/DS3/STS-1 LINE INTERFACE UNIT WITH SONET DESYNCRONIZER

REV. 1.0.2

108

DS3Clk/ CLK_OUT

I/O

DS3 Reference Clock Input/SFM Synthesizer Clock Output:

The function of this chip depends upon whether or not the XRT75R03D has

been configured to operate in the SFM Mode.

If NOT operating in the Single-Frequency Mode

If the XRT75R03D has NOT been configured to operate in the SFM Mode, and

if at least one channel of the XRT75R03D is configured in the DS3 Mode, then

a clock signal with a frequency of 44.736 MHz ± 20ppm must be applied to this

input pin.

If the XRT75R03D is not configured to operate in the SFM Mode and none of

the channels are to be operated in the DS3 Mode, tie this input signal to GND.

If operating in the Single-Frequency Mode

If the XRT75R03D is configured to operate in the SFM Mode, and if pin 107

(E3CLK/CLKEN) is pulled to a logic "High", then the SFM Clock Synthesizer

PLL generated line rate clock signal for Channel 1 will be output via this output

pin.

In this mode, this particular output pin can be used by the user's system as a

timing source.

109

STS-1Clk/ 12M

STS-1 Reference Clock Input/12.288MHz SFM Reference Clock Input:

The function of this pin depends upon whether or not the XRT75R03D has been

configured to operate in the SFM Mode.

If NOT operating in the Single-Frequency Mode

If the XRT75R03D has NOT been configured to operate in the SFM Mode and if

at least one channel is intended to operate in the STS-1 Mode, then the user

must supply a clock signal with a frequency of 51.84MHz ± 20ppm to this input

If the XRT75R03D is not to be operatedin the SFM Mode and none of the chan-

nels are to be operated in the STS-1 Mode, tie this input signal to GND.

If operating in the Single-Frequency Mode

If the XRT75R03D has been configured to operate in the SFM Mode a clock sig-

nal with a frequency of 12.288MHz ± 20ppm MUST be applied to this input pin.

The SFM Synthesizer will then synthesize all of the appropriate line rate fre-

quencies (e.g., 34.368MHz for E3, 44.736MHz for DS3, and 51.84MHz for STS-

1) based upon this 12.288MHz Reference Clock source.

SYSTEM-SIDE RECEIVE OUTPUT AND RECEIVE CONTROL PINS

PIN #SIGNAL NAME

TYPE

DESCRIPTION

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