XRT73R12_07 Datasheet, PDF (23/89 Pages) Exar Corporation – TWELVE CHANNEL E3/DS3/STS-1 LINE INTERFACE UNIT

XRT73R12
REV. 1.0.2
TWELVE CHANNEL E3/DS3/STS-1 LINE INTERFACE UNIT
2.1 Clock Distribution
Network cards that are designed to support multiple line rates which are not configured for single frequency
mode should ensure that a clock is applied to the DS3Clk input pin. For example: If the network card being
supplied to an ISP requires E3 only, the DS-3 input clock reference is still necessary to provide read and write
access to the internal microprocessor. Therefore, the E3 mode requires two input clock references. If
however, multiple line rates will not be supported, i.e. E3 only, then the DS3Clk input pin may be hard wire
connected to the E3Clk input pin.
FIGURE 4. CLOCK DISTRIBUTION CONGIFURED IN E3 MODE WITHOUT USING SFM
DS3Clk
E3Clk
Clock Synthesizer
µProcessor
CLKOUT_n
LOL_n
NOTE: For one input clock reference, the single frequency mode should be used.
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