BCM5722 Programmer’s Guide
10/15/07
Broadcom Corporation
Page 155 MDI Register Access Document 5722-PG101-R
MDI REGISTER ACCESS
Configuring physical devices and querying the status of physical devices are done via the MDIO interface (MDC and MDIO).
There are three modes in which the internal MII Management interface signals (MDC/MDIO) can be controlled for
communication with the internal transceiver registers. These modes are as follows:
• Autopolling Mode. Enabled by setting the Enable bit in the MAC Ethernet MI Mode register (see “MI Mode Register
(Offset 0x454)” on page 252). The device will poll for the link status bit in the transceiver.
• Command Control. Writing to the MI Communications register (see “MI Communication Register (Offset 0x44C)” on
page 251) directly to either read or write the transceiver registers.
• Register Control. When enabled, the host writes the MDC clock and data values into the MDI Control register (see “MDI
Control Register (Offset 0x6844)” on page 342). The values in the register directly control the interface signals. This
Mode is enabled by setting the MDI Select bit of the MDI Control register (Offset 0x6844).
Autopolling Mode has the lowest priority and it will be stalled any time there is an active operation through the MI
Communications register. Register Control Mode has the highest priority and When this mode is enabled, the MI
Communications register cannot be read or written.
OPERATIONAL CHARACTERISTICS
The interface between the MAC and physical devices is with the two signals of:
• MDIO clock (MDC)
• Bidirectional serial data (MDIO)
The details of the MDIO interface can be found in the IEEE 802.3 specification.
ACCESS METHODS
The MAC provides two methods to access the Physical Device registers via the MDIO interface:
• Traditional bit-bang method
• Auto-access method
Note: This procedure is PHY-independent. The MAC access to the PHY is the same for the entire NetXtreme
family.
To Next Page
Loading...