Intel manual PHY Signals, Networking Silicon -GD82559ER, Datasheet

Networking Silicon —GD82559ER

3.5PHY Signals

Symbol	Type	Name and Function
X1	A/I	Crystal Input One. X1 and X2 can be driven by an external 3.3 V 25
		MHz crystal. Otherwise, X1 may be driven by an external metal-oxide
		semiconductor (MOS) level 25 MHz oscillator when X2 is left floating.
		Crystal Input Two. X1 and X2 can be driven by an external 3.3 V 25
X2	A/O	MHz crystal. Otherwise, X1 may be driven by an external MOS level
		25 MHz oscillator when X2 is left floating.
		Analog Twisted Pair Ethernet Transmit Differential Pair. These
TDP		pins transmit the serial bit stream for transmission on the Unshielded
	A/O	Twisted Pair (UTP) cable. The current-driven differential driver can be
TDN		two-level (10BASE-T) or three-level (100BASE-TX) signals depending
		on the mode of operation. These signals interface directly with an
		isolation transformer.
RDP		Analog Twisted Pair Ethernet Receive Differential Pair. These pins
	A/I	receive the serial bit stream from the isolation transformer. The bit
RDN		stream can be two-level (10BASE-T) or three-level (100BASE-TX)
		signals depending on the mode of operation.
ACTLED#	OUT	Activity LED. The Activity LED pin indicates either transmit or receive
		activity. When activity is present, the activity LED is on; when no
		activity is present, the activity LED is off.
LILED#	OUT	Link Integrity LED. The Link Integrity LED pin indicates link integrity.
		If the link is valid in either 10 or 100 Mbps, the LED is on; if link is
		invalid, the LED is off.
SPEEDLED#	OUT	Speed LED. The Speed LED pin indicates the speed. The speed LED
		will be on at 100 Mbps and off at 10 Mbps.
		Reference Bias Resistor (100 Mbps). This pin controls the out
RBIAS100	B	envelope of the 82559ERER when transmitting in the 10 Mbps mode
		via the use of a pull-down resistor to ground. A value of 619 Ω pull-
		down resistor is adequate is most applications.
		Reference Bias Resistor (10 Mbps). This pin controls the out
RBIAS10	B	envelope of the 82559ER when transmitting in the 10 Mbps mode via
		the use of a pull-down resistor to ground. A value of 549 Ω pull-down
		resistor is adequate is most applications.
		Voltage Reference. This pin is connected to a 1.25 V ± 1% external
VREF	B	voltage reference generator. To use the internal voltage reference
		source, this pin should be left floating.

NOTE: 619 Ω and 549 Ω for the RBIAS100 and RBIAS10, respectively, are only a recommended values and should be fine tuned for various designs.

Datasheet 11