CS8904
Crystal LAN™ Quad Ethernet Transceiver
Port Loopback causes the 10BASE-T transmitter to
be idled and the 10BASE-T receiver to be
disconnected. In addition, data received from the
controller on the TxDATA pin is looped back on
the RxDATA pin to the controller. Both CD and
RxCLOCK are provided to synchronize the
transfer to the controller. Note that since the port is
isolated from the external Ethernet network,
collisions will not occur.
4.4 External Clock Oscillator
A 20-MHz quartz crystal or CMOS clock input is
required by the CS8904. If a CMOS clock input is
used, it should be connected the to XTAL1 pin,
with the XTAL2 pin left open. The clock signal
should be 20 MHz ±0.01% with a duty cycle
between 45% and 55%. The specifications for the
crystal are described in the External Clock section
of the DC CHARACTERISTICS Table.
CIRRUS LOGIC ADVANCED PRODUCT DATABOOK
DS191PP2
19
CIRRUS [ CIRRUS LOGIC ]
