Intel 82555 manual Media Access Control/Repeater Interface Control Pins

			Networking Silicon — 82555
Symbol	Pin	Type	Name and Function
RXC	90	O	Receive Clock. The Receive Clock may be either 25 MHz or 2.5 MHz
			depending on the 82555’s operating speed (25 MHz for 100 Mbps and 2.5
			MHz for 10 Mbps). The Receive Clock is recovered directly from incoming
			data and is continuous into the Media Access Controller (MAC). Thus, it must
			be resynchronized in 10 Mbps mode at the start of each incoming packet.
RXDV	86	O	Receive Data Valid. This signal indicates that the incoming data on the
			RSC[3:0] pins are valid.
RXERR	87	O	Receive Error. The RXERR signal indicates to the 82555 that an error has
			occurred during frame reception.
TXD3	71	I	Transmit Data. In 100 Mbps and 10 Mbps mode, data is transferred across
TXD2	70		these four lines one nibble at a time.
TXD1	69
TXD0	68
TXC	60	I/O	Transmit Clock. The Transmit Clock may be either 25 MHz or 2.5 MHz
			depending on the 82555’s operating speed (25 MHz for 100 Mbps and 2.5
			MHz for 10 Mbps). The Transmit Clock outputs a continuous clock into the
			MAC that is generated directly from the external clock source in DTE
			(adapter) mode. In repeater mode, the TXC is an input signal operating at
			either 25 MHz or 2.5 MHz depending on the operating speed, which is
			typically clocked by a receiver interface device.
TXEN	79	I	Transmit Enable. The Transmit Enable signal indicates to the 82555 that
			valid data is present on the TXD[3:0] pins.
TXERR	59	I	Transmit Error. The TXERR signal indicates to the 82555 that an error has
			occurred during transmissions of a frame.
CRS	82	O	Carrier Sense. The Carrier Sense signal indicates to the 82555 that traffic is
			present on the link. CRS is an asynchronous output signal.
COL	85	O	Collision Detect. The Collision Detect signal operates in half duplex mode
			and indicates to the 82555 that a collision has occurred on the link. COL is an
			asynchronous output signal to the controller.
MDIO	80	I/O	Management Data Input/Output. The MDIO signal is a bidirectional data pin
			for the Management Data Interface (MDI).
MDC	81	II	Management Data Clock. The MDC signal functions as a clock reference for
			the MDIO signal. MDC should operate at a maximum frequency of 2.5 MHz

3.5Media Access Control/Repeater Interface Control Pins

Symbol	Pin	Type	Name and Function
RXCONG	77	I	Receive Congestion. If the following conditions exist, the RXCONG is an
			active high and indicates an overrun on the controller receive side:
			• Full duplex PHY Base (Bay Technologies) flow control DTE (adapter)
			mode
			• Full duplex signal (FDX_N) is high
			• Full duplex technology is active through Auto-Negotiation
PORTEN	76	I	Port Enable. In repeater mode when the PORTEN signal is low, the following
			signals will be tri-stated: RXD[3:0], RXC, RXDV, and RXERR.

Datasheet 9