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Platform Notes: The hme FastEthernet Device Driver

Chapter 2 The hme Device Driver

The hme device driver handles the SUNW,hme device on these hardware devices:

This chapter gives a hardware overview of the SUNW,hme device, provides information on the operating speeds and modes for the SUNW,hme device, and discusses auto-negotiation, the internal transceiver, and the external transceiver for the hme device driver. Note that the external transceiver is not present on the SunSwift SBus Adapter or the SunSwift PCI Adapter.

Hardware Overview

The SUNW,hme device provides 10BASE-TX or 100BASE-T networking interfaces using the Fast Ethernet Parallel Port SCSI (FEPS) ASIC and an internal transceiver. The driver automatically sets the link speed to 10 or 100 Mbps and conforms to the 100BASE-T IEEE 802.3u Ethernet standard. The FEPS (SBus based) or PFEX (PCI-bus based) ASIC provides the SBus or PCI interface and Media Access Control (MAC) functions. The internal transceiver, which connects to an RJ-45 connector on all of the above hardware devices, provides the physical layer functions.

In addition to the RJ-45 connector, a Media Independent Interface (MII) connector, which is an Ultra DB 40 connector, is also provided on Sun systems. The MII connects to an external transceiver that may use any physical media, such as copper or fiber as specified in the 100BASE-TX standard. When an external transceiver is connected to the MII, the driver selects the external transceiver and disables the internal transceiver. The external transceiver may also support the 100BASE-T4 standard, which allows the link to operate in 100 Mbps speed using four pairs of category 3 or better cable.

Operating Speeds and Modes

You can operate the link in any of the following speeds and modes with the SUNW, hme device:

The 100BASE-T standard, IEEE 802.3u Ethernet Standard, describes these speeds and modes.

Auto-Negotiation

The auto-negotiation protocol, as specified by the 100BASE-T standard, selects the operation mode (half-duplex or full-duplex) at boot time or when the link state changes (the link goes down or tried to come up). The auto-negotiation protocol also selects the speed and the full duplex or half duplex mode.

The auto-negotiation protocol does the following:

The link partner is the networking device (system, Ethernet hub, or Ethernet switch) at the other end of the link or cable. If the SUNW,hme device is connected to a remote system or interface that is not capable of auto-negotiation, the system automatically selects the correct speed and half-duplex mode.

If adapters or systems are connected to a link partner and the auto-negotiation protocol fails to operate successfully, you can configure the device so it does not use this protocol. This forces the driver to set up the link in the mode and speed that you choose instead of using the auto-negotiation protocol.

Internal Transceiver

The internal transceiver is a feature supported by the driver and is capable of all the operating speeds and modes (except the 100BASE-T4 mode) listed in the section "Operating Speeds and Modes"," earlier in this chapter. When the internal transceiver is used, the default is auto-negotation by the hme driver, which automatically selects the speed and mode of the link. The internal transceiver performs auto-negotiation with the remote end of the link (link partner) to select a common mode of operation.

The internal transceiver also supports a forced mode of operation. This is where the user selects the speed and mode using the ndd utility, the /etc/system file, or the hme.conf file. The ndd utility makes calls to the hme driver to choose the speed and mode.

External Transceiver

When an external transceiver (not present on the SunSwift SBus Adapter) is connected to the MII interface, the driver selects the external transceiver for networking operations.

You can also manually select the speed and mode of the link. For example, two transceivers might not support the same mode and speed. Therefore, you must select the highest mode and speed that both transceivers support using the ndd utility. See the list of operating speeds and modes in the section, "Operating Speeds and Modes"," in this chapter.