Micrel, Inc.
KSZ8041NL/RNL
Carrier Sense/Receive Data Valid (CRS_DV)
CRS_DV is asserted by the PHY when the receive medium is non-idle. It is asserted asynchronously on detection of
carrier. This is when squelch is passed in 10Mbps mode, and when 2 non-contiguous zeroes in 10 bits are detected in
100Mbps mode. Loss of carrier results in the de-assertion of CRS_DV.
So long as carrier detection criteria are met, CRS_DV remains asserted continuously from the first recovered di-bit of the
frame through the final recovered di-bit, and it is negated prior to the first REF_CLK that follows the final di-bit. The data
on RXD[1:0] is considered valid once CRS_DV is asserted. However, since the assertion of CRS_DV is asynchronous
relative to REF_CLK, the data on RXD[1:0] is "00" until proper receive signal decoding takes place.
Receive Data [1:0] (RXD[1:0])
RXD[1:0] transitions synchronously to REF_CLK. For each clock period in which CRS_DV is asserted, RXD[1:0] transfers
two bits of recovered data from the PHY. RXD[1:0] is "00" to indicate idle when CRS_DV is de-asserted. Values other
than “00” on RXD[1:0] while CRS_DV is de-asserted are ignored by the MAC.
Receive Error (RX_ER)
RX_ER is asserted for one or more REF_CLK periods to indicate that a Symbol Error (e.g. a coding error that a PHY is
capable of detecting, and that may otherwise be undetectable by the MAC sub-layer) was detected somewhere in the
frame presently being transferred from the PHY.
RX_ER transitions synchronously with respect to REF_CLK. While CRS_DV is de-asserted, RX_ER has no effect on the
MAC.
Collision Detection
The MAC regenerates the COL signal of the MII from TX_EN and CRS_DV.
RMII Signal Diagram
The KSZ8041NL RMII pin connections to the MAC are shown in Figure 2.
Figure 2. KSZ8041NL RMII Interface
September 2010
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M9999-090910-1.4
MICROCHIP [ MICROCHIP ]
