Datasheet

Micrel, Inc. KS8999
January 2005
23
KS8999
MII Interface Operation
The MII (Media Independent Interface) operates in either a MAC or PHY mode. In the MAC mode, the KS8999 MII
acts like a MAC and in the PHY mode, it acts like a PHY device. This interface is specified by the IEEE 802.3
committee and provides a common interface between physical layer and MAC layer devices. There are two distinct
groups, one being for transmission and the other for receiving. The table below describes the signals used in this
interface in MAC and PHY modes.
PHY Mode Connection MAC Mode Connection
External MAC
Controller Signals
KS8999 PHY
Signals
Description
External PHY
Signals
KS8999 MAC Signals
MTXEN MTXEN Transmit enable MTXEN MRXDV
MTXER MTXER Transmit error MTXER Not used
MTXD3 MTXD[3] Transmit data bit 3 MTXD3 MRXD[3]
MTXD2 MTXD[2] Transmit data bit 2 MTXD2 MRXD[2]
MTXD1 MTXD[1] Transmit data bit 1 MTXD1 MRXD[1]
MTXD0 MTXD[0] Transmit data bit 0 MTXD0 MRXD[0]
MTXC MTXC Transmit clock MTXC MTXC
MCOL MCOL Collision detection MCOL MCOL
MCRS MCRS Carrier sense MCRS MCRS
MRXDV MRXDV Receive data valid MRXDV SMTXEN
MRXER Not used Receive error MRXER MTXER
MRXD3 MRXD[3] Receive data bit 3 MRXD3 MTXD[3]
MRXD2 MRXD[2] Receive data bit 2 MRXD2 MTXD[2]
MRXD1 MRXD[1] Receive data bit 1 MRXD1 MTXD[1]
MRXD0 MRXD[0] Receive data bit 0 MRXD0 MTXD[0]
MRXC MRXC Receive clock MRXC MRXC
Table 1. MII Signals
This interface is a nibble wide data interface and therefore runs at _ the network bit rate (not encoded). Additional
signals on the transmit side indicate when data is valid or when an error occurs during transmission. Likewise, the
receive side has indicators that convey when the data is valid and without physical layer errors.
For half-duplex operation there is a signal that indicates a collision has occurred during transmission.