82551IT — Networking Silicon
3.3
Hardware Integrity Support
Cabling problems are a common cause for network downtime situations. Hardware Integrity
(HWI) can help reduce this by locating cabling problems. It uses transmission line theory to
measure the arrival time and electrical characteristics of the wave reflected from an incident test
wave launched on the media. With these measurements, opens, shorts, and degraded cable quality
can be located along the wire.
HWI is controlled and activated by software. The Hardware Integrity Control, register 29 of the
MDI Registers, is used for activating HWI (Section 9.3.14, “Register 29: Hardware Integrity
Control Register”).
3.4
Management Data Interface MDI/MDI-X Feature
The 82551IT controller MDI/MDI-X feature provides the ability to automatically detect the
required cable connection type and configure the controller-side MAU to the cable type. This
feature effectively allows all properly wired Ethernet cables usable with any Ethernet device to be
connected to the 82551IT without any additional external logic.
This advanced feature enables auto-correction of incorrect cabling with respect to cross-over
versus straight-through cables. The 82551IT 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 1 lists the connections for both straight-through and cross-over RJ-45 ports for comparison.
Table 1. RJ-45 Connections
RJ-45
Contact
Straight-Through
MDI Signala
Cross-Over MDIX
Signalb
1
TD+
RD+
2
3
4
5
6
7
8
TD-
RD-
RD+
TD+
Not Used
Not Used
RD-
Not Used
Not Used
TD-
Not Used
Not Used
Not Used
Not Used
a.
b.
Straight-through connections used on DTE applications.
Cross-over connections used on Hub and Switch applications.
6
Datasheet
INTEL [ INTEL ]
