7.0 FUNCTIONAL SPECIFICATION The PD11394P21 requires only an external 24.576 MHz crystal as a reference. An external clock can be provided instead of a crystal. An internal oscillator drives an internal phase-locked loop (PLL), which generates the required 393.216 MHz reference signal. This reference signal is internally divided to provide the clock signals used to control transmission of the outbound encoded Strobe and Data information. A 49.152 MHz clock signal, supplied to the associated LLC for synchronization of the two chips, is used for resynchronization of the received data. The Power Down (PD) function, when enabled by asserting the PD terminal high, stops operation of the PLL and disables all circuits except the cable bias detectors at the TPB terminals. The port transmitter circuitry and the receiver circuitry are also disabled when the port is disabled, suspended, or disconnected.
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