TLK100_11 Datasheet, PDF (14/88 Pages) Texas Instruments – Industrial Temp, Single Port 10/100 Mb/s Ethernet Physical Layer Transceiver

TLK100
SLLS931B – AUGUST 2009 – REVISED DECEMBER 2009
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The Auto-Negotiation function can also be controlled by internal register access using registers as defined
by the IEEE 802.3u specification. For further detail regarding Auto-Negotiation, see Clause 28 of the IEEE
802.3u specification.
3.2 Auto-MDIX
The TLK100 device automatically determines whether or not it needs to cross over between pairs so that
an external crossover cable is not required. If the TLK100 device interoperates with a device that
implements MDI/MDIX crossover, a random algorithm as described in IEEE 802.3 determines which
device performs the crossover.
Auto-MDIX is enabled by default and can be configured via jumper or via PHYCR (0x10h) register, bits
[6:5].
The crossover can be manually forced through bit 5 of PHYCR (0x10h) register. Neither Auto-Negotiation
nor Auto-MDIX is required to be enabled in forcing crossover of the MDI pairs.
Auto-MDIX can be used in the forced 100BT mode but not in the forced MDIX mode. As in modern
networks all the nodes are 100BT, having the Auto-MDIX working in the forced 100BT mode will resolve
the link faster without the need for the long Auto-Negotiation.
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