82562GT Datasheet, PDF (13/46 Pages) Intel Corporation – 10/100 Mbps Platform LAN Connect (PLC)

Networking Silicon — 82562GT
3.1.2
3.2
Enhanced Tx Mode
The enhanced Tx mode speeds up the rise and fall times of the 100 Mb signal. This was done so the
82562GT can have improved IEEE PHY conformance requirements over a more capacitive Analog
Front End (AFE); usually caused by long traces or differential switches that customers use, usually
on mobile platforms. However, running an 82562GT device in enhanced mode increases the
radiated emissions seen from the LAN solution. The increase in radiated emissions may or may not
impact the DUT’s ability to pass regulatory requirements, as it will depend largely on the design of
the AFE. The enhanced mode should only be used when 100Base-TX rise/fall times cannot be met
in the normal 82562GT mode. Consult an Intel representative if you are considering using this
mode.
Management Data Interface MDI/MDI-X
MDI/MDI-X provides the ability to automatically detect the required cable connection type and
configure the controller-side MAU to the cable type. MDI/MDI-X effectively allows all properly
wired Ethernet cables usable with any Ethernet device to be connected to the 82562GT without any
additional external logic.
MDI/MDI-X enables auto-correction of incorrect cabling with respect to cross-over versus
straight-through cables. The 82562GT can identify the cable connection type and adjust its MDI
port to the cable by switching between the TD and RD pairs. The auto-switching is done prior to
the start of the hardware auto negotiation algorithm.
In a standard straight-through RJ-45 port configuration, the transmit pair is on contacts 1 and 2, and
the receive pair on contacts 3 and 6. These are defined by Clause 23.7.1 of the IEEE 802.3u
standard.
Table 4 lists the connections for both straight-through and cross-over RJ-45 ports for comparison.
Table 4. RJ-45 Connections
RJ-45
Contact
Straight-Through
MDI Signal^a
Cross-Over MDIX
Signal^b
1
TD+
RD+
2
TD-
RD-
3
RD+
TD+
4
Not Used
Not Used
5
Not Used
Not Used
6
RD-
TD-
7
Not Used
Not Used
8
Not Used
Not Used
a. Straight-through connections used on Data Terminal Equipment
(DTE) applications.
b. Cross-over connections used on Hub and Switch applications.
Datasheet
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