
Chapter 3
Functional Operation
109
24674
Rev. 3.00
April 2003
AMD-8111 HyperTransport I/O Hub Data Sheet
AMD Preliminary Information
the network controller to the external PHY and is synchronous with the rising edge of TX_CLK. The
transmit process starts when the network controller asserts TX_EN, which indicates to the external
PHY that the data on TXD(3:0) is valid.
IEEE standard 802.3 provides a mechanism for signalling unrecoverable errors through the MII to the
external PHY with the TX_ER output pin. The external PHY responds to this error by generating a
TX coding error on the current transmitted frame. The network controller does not use this method of
signaling errors on the transmit side. Instead, if the network controller detects a transmit error, it
inverts the FCS to generate an invalid FCS. Since the network controller does not implement the
TX_ER function, the TX_ER pin on the external PHY device should be connected to VSS.
3.10.11.2
MII Receive Interface
The MII receive clock is also generated by the external PHY and is sent to the network controller on
the RX_CLK input pin. The clock can run at 25 MHz or 2.5 MHz, depending on the speed of the
network to which the external PHY is attached.
Figure 25.
Media Independent Interface
The receive process starts when RX_DV is asserted. RX_DV must remain asserted until the end of the
receive frame. If the external PHY device detects errors in the currently received frame, it asserts the
RX_ER signal. RX_ER can be used to signal special conditions
out of band
when RX_DV is not
asserted. Two defined out-of-band conditions for this are the 100BASE-TX signaling of
bad
Start of
Frame Delimiter and the 100BASE-T4 indication of illegal code group before the receiver has
synchronized with the incoming data. The network controller does not respond to these conditions.
All
out of band
conditions are currently treated as NULL events. Certain
in-band
non-IEEE 802.3-
compliant flow control sequences may cause erratic behavior for the network controller. Consult the
switch/bridge/router/hub manual to disable the
in-band
flow control sequences if they are being used.
4
RXD(3:0)
RX_DV
RX_ER
RX_CLK
CRS
4
TXD(3:0)
TX_EN
M
COL
Receive Signals
Transmit Signals
Management Port Signals
Network Status Signals
TX_CLK
MDIO
MDC
Network
Controller