Micrel, Inc.
KSZ8041NL/RNL
RMII Signal Definition
The Tables 3 and 4 describe the RMII signals for KSZ8041NL and KSZ8041RNL. Refer to RMII Specification for detailed
information.
Direction
(with respect to PHY,
KSZ8041NL signal)
RMII
Signal Name
Direction
(with respect to MAC)
Description
REF_CLK
Input
Input, or Output
Synchronous 50 MHz clock reference for
receive, transmit and control interface
TX_EN
Input
Output
Transmit Enable
TXD[1:0]
CRS_DV
RXD[1:0]
RX_ER
Input
Output
Transmit Data [1:0]
Carrier Sense/Receive Data Valid
Receive Data [1:0]
Receive Error
Output
Output
Output
Input
Input
Input, or (not required)
Table 3. RMII Signal Description – KSZ8041NL
Direction
(with respect to PHY,
KSZ8041RNL signal)
RMII
Signal Name
Direction
(with respect to MAC)
Description
REF_CLK
Output
Input
Synchronous 50 MHz clock reference for
receive, transmit and control interface
TX_EN
Input
Output
Transmit Enable
TXD[1:0]
CRS_DV
RXD[1:0]
RX_ER
Input
Output
Transmit Data [1:0]
Carrier Sense/Receive Data Valid
Receive Data [1:0]
Receive Error
Output
Output
Output
Input
Input
Input, or (not required)
Table 4. RMII Signal Description – KSZ8041RNL
Reference Clock (REF_CLK)
REF_CLK is a continuous 50MHz clock that provides the timing reference for TX_EN, TXD[1:0], CRS_DV, RXD[1:0], and
RX_ER.
The KSZ8041NL inputs the 50MHz REF_CLK from the MAC or system board.
The KSZ8041RNL generates the 50MHz RMII REF_CLK and outputs it to the MAC.
Transmit Enable (TX_EN)
TX_EN indicates that the MAC is presenting di-bits on TXD[1:0] for transmission. It is asserted synchronously with the first
nibble of the preamble and remains asserted while all di-bits to be transmitted are presented on the RMII, and is negated
prior to the first REF_CLK following the final di-bit of a frame.
TX_EN transitions synchronously with respect to REF_CLK.
Transmit Data [1:0] (TXD[1:0])
TXD[1:0] transitions synchronously with respect to REF_CLK. When TX_EN is asserted, TXD[1:0] are accepted for
transmission by the PHY. TXD[1:0] is ”00” to indicate idle when TX_EN is de-asserted. Values other than “00” on TXD[1:0]
while TX_EN is de-asserted are ignored by the PHY.
September 2010
26
M9999-090910-1.4
MICREL [ MICREL SEMICONDUCTOR ]
