Kontron COMe Starterkit Eval T2 - Manual (Page 71)

COM Express Interfaces
Table 17: LAN Interface LED Function
LED-Function LED Color# LED State Description
Link Speed Green / Orange Off 10 Mbps link speed
Green 100 Mbps link speed
Orange 1000 Mbps link speed
Link Status & Activity Yellow Off No Link
Steady On Link established, no activity detected
Blinking Link established, activity detected
2.7.1.2. LAN 1 and 2 shared with IDE
The Type 2 COM Express Module only provides one LAN port to the carrier. Type 3 and 5 COM
Express Modules provide two additional 10/100/1000BASE-T Gigabit Ethernet ports in place of
the IDE port, and Type 5 Module definitions include an option to support 10 Gigabit Ethernet port
operation.
This Design Guide does not explicitly define Carrier Board support for the Type 3 and 5 COM
Express Modules. However, it is recommended that a carrier supporting one of those Modules
should follow the guidelines for the LAN 0 port carrier circuit in this section when defining the
LAN 1 and 2 port carrier circuits.
2.7.1.3. PHY / Magnetics Connections
The COM Express Module specification partitions the IEEE 802.3 PHY / MDI interface circuit
resources between the Module and carrier, with the PHY located on the Module and the coupling
magnetics located on the carrier, preferably physically integrated in the RJ-45 receptacle housing
associated with the port. Section 5.4.5 of the COM Express Module specification shows this
circuit topology and provides a high level signal attenuation budget for Ethernet signals
traversing this circuit.
In order to meet the signal performance requirements for MDI signals as defined in the IEEE
802.3-2005 specification and to ensure maximum interoperability of COM Express Modules and
carriers, the PHY / Magnetics circuit should be implemented using the following guidelines:
●
The carrier should provide a full 8-wire (10/100/1000BASE-T) interface circuit to the COM
Express Module
●
Any secondary side resistive terminations required by the Module PHY will be present on the
Module and are not on the Carrier
●
The center tap reference signal should be routed from the COM Express Module connector to
the secondary side center tap of each transformer as defined in the IEEE 802.3-2005
specification, without any series resistance or impedance circuits
●
The Carrier Board design should utilize a coupling transformer capable of interoperating with
the largest possible number of PHY devices
● The Carrier Board design should have the primary side and secondary side center tap
termination components (75 Ω resistors and 100 nF capacitors, respectively) placed
physically as close to the coupling transformer as possible
● The coupling transformer should be placed no further than 100mm (3.9”) from the COM
Express Module connector on the Carrier Board.
●
It is recommended that the carrier use a RJ-45 connector with an integrated transformer.
However, if a discrete coupling transformer is used, the transformer must be placed no further
than 25mm (1.0”) from the RJ-45 receptacle.
PICMG ® COM Express ® Carrier Board Design Guide Rev. 2.0 / December 6, 2013
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