lxt972a Intel Corporation, lxt972a Datasheet - Page 21

• Manufacturer Part Number: lxt972a
• Description: 3.3v Dual-speed Fast Ethernet Transceiver Datasheet
• Manufacturer: Intel Corporation

3.4
3.4.1
3.4.2
Datasheet
Initialization
When the LXT972A is first powered on, reset, or encounters a link failure state, it checks the
MDIO register configuration bits to determine the line speed and operating conditions to use for
the network link. The configuration bits may be set by the Hardware Control or MDIO interface as
shown in
MDIO Control Mode
In the MDIO Control mode, the LXT972A reads the Hardware Control Interface pins to set the
initial (default) values of the MDIO registers. Once the initial values are set, bit control reverts to
the MDIO interface.
Hardware Control Mode
In the Hardware Control Mode, LXT972A disables direct write operations to the MDIO registers
via the MDIO Interface. On power-up or hardware reset the LXT972A reads the Hardware Control
Interface pins and sets the MDIO registers accordingly.
The following modes are available using either Hardware Control or MDIO Control:
When the network link is forced to a specific configuration, the LXT972A immediately begins
operating the network interface as commanded. When auto-negotiation is enabled, the LXT972A
begins the auto-negotiation / parallel-detection operation.
•
•
Force network link operation to:
100TX, Full-Duplex.
100TX, Half-Duplex.
10BASE-T, Full-Duplex.
10BASE-T, Half-Duplex.
Allow auto-negotiation / parallel-detection.
Figure
6.
3.3V Dual-Speed Fast Ethernet Transceiver Datasheet — LXT972A
21