COM Express® Carrier Board Design Guide
19
2.4 LAN
In general, COM Express Modules provide at least one LAN port. The 8-wire 10/100/1000BASE-T
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
10/100BASE-TX vs 10/100/1000BASE-T operation. The carrier may also support a 4-wire
10/100BASE-TX interface from the COM Express Module on an exception basis.
2.4.1 Signal Definitions
The LAN interface of the COM Express Module has 4 pairs of low voltage differential pair signals
designated from 'GBE0_MDI0' (+ and -) to 'GBE0_MDI3' (+ and -) plus additional control signals for
link activity indicators. The signals can connect to a 10/100/1000BASE-T RJ45 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, as listed below.
Table 4: LAN Interface Signal Descriptions
Signal
Pin#
Description
I/O
Remarks
GB
GBE0_MDI0-
A13
A12
Media Dependent Interface (MDI) differential pair
0. The MDI can operate in 1000, 100, and
10Mbit/sec modes.
I/O GBE
This signal pair is used for all
modes.
GB
GBE0_MDI1-
A10
A9
Media Dependent Interface (MDI) differential pair
1. The MDI can operate in 1000, 100, and
10Mbit/sec modes.
I/O GBE
This signal pair is used for all
modes.
GB
GBE0_MDI2-
A7
A6
Media Dependent Interface (MDI) differential pair
2. The MDI can operate in 1000, 100, and
10Mbit/sec modes.
I/O GBE
This signal pair is only used
for 1000Mbit/sec Gigabit
Ethernet mode.
GB
GBE0_MDI3-
A3
A2
Media Dependent Interface (MDI) differential pair
3. The MDI can operate in 1000, 100, and
10Mbit/sec modes.
I/O GBE
This signal pair is only used
for 1000Mbit/sec Gigabit
Ethernet mode.
GBE0_CTREF
A14
Reference voltage for Carrier Board Ethernet
channel 0 magnetics center tap.
REF
GBE0_LINK#
A8
Ethernet controller 0 link indicator, active low.
O 3.3V
Suspend
OD CMOS
GBE0_LINK100#
A4
Ethernet controller 0 100Mbit/sec link indicator,
active low.
O 3.3V
Suspend
OD CMOS
GBE0_LINK1000#
A5
Ethernet controller 0 1000Mbit/sec link indicator,
active low.
O 3.3V
Suspend
OD CMOS
GBE0_ACT#
B2
Ethernet controller 0 activity indicator, active low.
O 3.3V
Suspend
OD CMOS
Summary of Contents for ET976
Page 1: ...COM EXPRESS CARRIER BOARD DESIGN GUIDE Version 1 0 January 2022...
Page 11: ...COM Express Carrier Board Design Guide 5 Figure 3 PCI Express x4 Slot Example...
Page 12: ...6 COM Express Carrier Board Design Guide Figure 4 PCIe Mini Card Reference Circuitry...
Page 19: ...COM Express Carrier Board Design Guide 13 Figure 7 HDMI Example 1...
Page 20: ...14 COM Express Carrier Board Design Guide Figure 7 HDMI Example 2...
Page 21: ...COM Express Carrier Board Design Guide 15 Figure 8 DVI Example 1...
Page 22: ...16 COM Express Carrier Board Design Guide Figure 8 DVI Example 2...
Page 31: ...COM Express Carrier Board Design Guide 25 Figure 12 USB 3 0 Example 2...
Page 37: ...COM Express Carrier Board Design Guide 31 Figure 14 LVDS Reference Schematic 2...
Page 44: ...38 COM Express Carrier Board Design Guide Figure 16 VGA Reference Schematics 2...
Page 48: ...42 COM Express Carrier Board Design Guide Figure 18 HDA Example Schematic 2...
Page 52: ...46 COM Express Carrier Board Design Guide Figure 19 LPC Super I O Example 2...
Page 61: ...COM Express Carrier Board Design Guide 55 Figure 24 General Purpose Serial Port Example 2...
Page 70: ...64 COM Express Carrier Board Design Guide Figure 28 PWRBTN and SYS_RESET Circuitry...
Page 84: ...78 COM Express Carrier Board Design Guide Chapter 4 Carrier Board PCB Layout Guidelines...
