User`s manual

RTD Embedded Technologies, Inc. | www.rtd.com 17 LAN25255HR/LAN35255HR User’s Manual
BroadCom Gig-Ethernet Switch 4.2
The main component of the LAN25255HR is the BroadCom BCM53115 Gigabit Ethernet switch. This is an industrial temperature rated, 5 port
Gigabit Ethernet switch. This switch contains 5 full-duplex 10/100/1000 BASE-TX Ethernet transceivers for network interfacing. One of these
ports is used in conjunction with the WG82574IT for a host port. This allows the LAN25255HR to work as its own mini-server in a stacked
system. In a stand-alone system the BroadCom switch acts as a basic Ethernet switch. Any port can be used as an upstream port to supply a
connection to the 3 other ports.
Jumbo Frame Support 4.3
The Broadcom Ethernet switch is capable of forwarding Ethernet frames up to 9720 bytes. The maximum frame size supported by the Intel
Ethernet controller is 9014 bytes. To use Jumbo frames, it must be enabled in the Ethernet Controller driver settings (e.g. via the Device
Manager in Windows). Until this is enabled, the Intel controller will drop any Jumbo frames it receives. Note that to use Jumbo frames
effectively, all devices connected to the network must have Jumbo frames enabled, AND must agree on the frame size (mismatched frame
sizes will result in dropped packets).
Intel WG82574IT Gigabit Ethernet Controller 4.4
The LAN25255HR has an onboard Gigabit Ethernet controller, the Intel WG82574IT. The Intel WG82574IT is an industrial rated Gigabit
Ethernet controller which features Auto-Crossover for MDI/MDI-X, 9014 byte Jumbo Frame support, 40KB packet buffer size and IPv4/6
support. This controller connects to the host CPU through a x1 PCI Express link on the PCIe/104 connector and interfaces through the fifth
port of the Ethernet switch to provide a host port for stacked systems.
Onboard LEDs and External LED Connectors 4.5
The LAN25255 has onboard LEDs for each of the five Ethernet ports on the board. The setting for the onboard LEDs is to show link activity,
status and speed at 10/100/1000M. To bring the LEDs out of an enclosed system, there are two 0.1 inch DIL connectors (CN14 & CN15) that
can be wired to external LED circuitry. These signals are can source or sink 24 mA and the connector has jumper options for 3.3 volt or ground
to facilitate external LED configuration.