Micrel, Inc.
KSZ8041NL
MII Signal Definition
The following table describes the MII signals. Refer to Clause 22 of the IEEE 802.3u Specification for detailed information.
Direction
(with respect to PHY,
KSZ8041NL signal)
MII
Direction
(with respect to MAC)
Description
Signal Name
TXC
Output
Input
Transmit Clock
(2.5MHz for 10Mbps; 25MHz for 100Mbps)
TXEN
TXD[3:0]
RXC
Input
Output
Output
Input
Transmit Enable
Input
Transmit Data [3:0]
Receive Clock
Output
(2.5MHz for 10Mbps; 25MHz for 100Mbps)
Receive Data Valid
Receive Data [3:0]
Receive Error
RXDV
RXD[3:0]
RXER
CRS
Output
Output
Output
Output
Output
Input
Input
Input, or (not required)
Input
Input
Carrier Sense
COL
Collision Detection
Table 2. MII Signal Definition
Transmit Clock (TXC)
TXC is sourced by the PHY. It is a continuous clock that provides the timing reference for TXEN and TXD[3:0].
TXC is 2.5MHz for 10Mbps operation and 25MHz for 100Mbps operation.
Transmit Enable (TXEN)
TXEN indicates the MAC is presenting nibbles on TXD[3:0] for transmission. It is asserted synchronously with the first
nibble of the preamble and remains asserted while all nibbles to be transmitted are presented on the MII, and is negated
prior to the first TXC following the final nibble of a frame.
TXEN transitions synchronously with respect to TXC.
Transmit Data [3:0] (TXD[3:0])
TXD[3:0] transitions synchronously with respect to TXC. When TXEN is asserted, TXD[3:0] are accepted for transmission
by the PHY. TXD[3:0] is ”00” to indicate idle when TXEN is de-asserted. Values other than “00” on TXD[3:0] while TXEN
is de-asserted are ignored by the PHY.
Receive Clock (RXC)
RXC provides the timing reference for RXDV, RXD[3:0], and RXER.
•
In 10Mbps mode, RXC is recovered from the line while carrier is active. RXC is derived from the PHY’s reference
clock when the line is idle, or link is down.
•
In 100Mbps mode, RXC is continuously recovered from the line. If link is down, RXC is derived from the PHY’s
reference clock.
RXC is 2.5MHz for 10Mbps operation and 25MHz for 100Mbps operation.
July 2008
17
M9999-071808-1.2
MICROCHIP [ MICROCHIP ]
