307013-003 Datasheet, PDF (113/848 Pages) Intel Corporation – Intel I/O Controller Hub 7

Functional Description
5.3.3
5.3.3.1
5.3.3.2
5.3.3.3
5.3.4
CSMA/CD Unit
The ICH7 integrated LAN controller CSMA/CD unit implements both the IEEE 802.3
Ethernet 10 Mbps and IEEE 802.3u Fast Ethernet 100 Mbps standards. It performs all
the CSMA/CD protocol functions (e.g., transmission, reception, collision handling, etc.).
The LAN controller CSMA/CD unit interfaces to the 82562ET/EM/EZ/EX 10/100 Mbps
Ethernet through the ICH7’s LAN Connect interface signals.
Full Duplex
When operating in full-duplex mode, the LAN controller can transmit and receive
frames simultaneously. Transmission starts regardless of the state of the internal
receive path. Reception starts when the platform LAN Connect component detects a
valid frame on its receive differential pair. The ICH7 integrated LAN controller also
supports the IEEE 802.3x flow control standard, when in full-duplex mode.
The LAN controller operates in either half-duplex mode or full-duplex mode. For proper
operation, both the LAN controller CSMA/CD module and the discrete platform LAN
Connect component must be set to the same duplex mode. The CSMA duplex mode is
set by the LAN Controller Configure command or forced by automatically tracking the
mode in the platform LAN Connect component. Following reset, the CSMA defaults to
automatically track the platform LAN Connect component duplex mode.
The selection of duplex operation (full or half) and flow control is done in two levels:
MAC and LAN Connect.
Flow Control
The LAN controller supports IEEE 802.3x frame-based flow control frames only in both
full duplex and half duplex switched environments. The LAN controller flow control
feature is not intended to be used in shared media environments.
Flow control is optional in full-duplex mode and is selected through software
configuration. There are three modes of flow control that can be selected: frame-based
transmit flow control, frame-based receive flow control, and none.
VLAN Support
The LAN controller supports the IEEE 802.1 standard VLAN. All VLAN flows will be
implemented by software. The LAN controller supports the reception of long frames,
specifically frames longer than 1518 bytes, including the CRC, if software sets the Long
Receive OK bit in the Configuration command. Otherwise, “long” frames are discarded.
Media Management Interface
The management interface allows the processor to control the platform LAN Connect
component via a control register in the ICH7 integrated LAN controller. This allows the
software driver to place the platform LAN Connect in specific modes (e.g., full duplex,
loopback, power down, etc.) without the need for specific hardware pins to select the
desired mode. This structure allows the LAN controller to query the platform LAN
Connect component for status of the link. This register is the MDI Control Register and
resides at offset 10h in the LAN controller CSR. The MDI registers reside within the
platform LAN Connect component, and are described in detail in the platform LAN
Connect component’s datasheet. The processor writes commands to this register and
the LAN controller reads or writes the control/status parameters to the platform LAN
Connect component through the MDI register.
Intel ^® ICH7 Family Datasheet
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