Datasheet

 2017 Microchip Technology Inc. DS00002436B-page 27
KSZ8041TL/FTL/MLL
3.16.5 COLLISION DETECTION
Collisions occur when CRS and TX_EN are simultaneously asserted. The MAC regenerates the MII collision signal from
CRS and TX_EN.
3.17 HP Auto MDI/MDI-X
HP Auto MDI/MDI-X configuration eliminates the confusion of whether to use a straight cable or a crossover cable
between the KSZ8041TL/FTL/MLL and its link partner. This feature allows the KSZ8041TL/FTL/MLL to use either type
of cable to connect with a link partner that is in either MDI or MDI-X mode. The auto-sense function detects transmit and
receive pairs from the link partner, and then assigns transmit and receive pairs of the KSZ8041TL/FTL/MLL accordingly.
HP Auto MDI/MDI-X is enabled by default. It is disabled by writing a one to register 1F bit 13. MDI and MDI-X mode is
selected by register 1F bit 14 if HP Auto MDI/MDI-X is disabled.
An isolation transformer with symmetrical transmit and receive data paths is recommended to support auto MDI/MDI-X.
The IEEE 802.3 Standard defines MDI and MDI-X as follow:
FIGURE 3-3: SMII RECEIVE DATA/CONTROL SEGMENT
TABLE 3-7: SMII RX BIT DESCRIPTION
SMII RX Bit Description
CRS Carrier Sense
RX_DV Receive Data Valid
RXD[0:7] Encoded Data
See Table 3-8.
TABLE 3-8: SMII RXD[0:7] ENCODING TABLE
CRS RX_DV RXD0 RXD1 RXD2 RXD3 RXD4 RXD5 RXD6 RXD7
X0RX_ER
from pre-
vious
frame
Speed
0=10M
1=100M
Duplex
0=Half
1=Full
Link
0=Down
1=Up
Jabber
0=No
1=Yes
Upper
Nibble
0=Invalid
1=Valid
False
Carrier
Detected
1
X 1 One Data Byte
CRS RX_DV RXD0 RXD1 RXD2 RXD3 RXD4 RXD5 RXD6 RXD7
CLOCK
SYNC
RX