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5 LAN
All COM Express modules provide at least one LAN port. The 8-wire 10/100/1000BaseT Gigabit
Ethernet interface compliant to the IEEE 802.3-2005 Specification is the preferred interface for this
port, with the COM Express module PHY responsible for implementing auto negotiation of
10/100BaseTX versus 10/100/1000BaseT operation. The carrier may also support a 4-wire
10/100BaseTX interface from the COM Express nodule on an exception basis. The magnetic circuit
should be implemented on the carrier board.
5.1 LAN Signals Definition
The LAN interface of the COM Express module consists of four pairs of low voltage differential pair
signals designated from GBE0_MDI0 (+ and -) to GBE0_MDI3 (+ and -), plus additional control signals
for link activity indicators. These signals can be used to connect to a 10/100/1000BaseT RJ-45
connector with integrated or external isolation magnetics on the carrier board. The corresponding LAN
differential pair and control signals can be found on rows A and B of the module's connector. See Table
6.
Table 6 LAN Interface Signal Description
COM Express Carrier Type 2
Design Guide
Page 37 of 103
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