
MII PHY Registers
2-16
The status register (GEN_sts in ThunderLAN products) includes bits to identify
the technology supported by the PHY. This technology includes protocol and
duplex abilities. It indicates link, jabber, and autoconfiguration completion. Bit
0 of the status register also indicates whether the extended register set is sup-
ported.
The PHY identifier registers (GEN_id_hi/GEN_id_lo in ThunderLAN products)
contain an identifier code for the silicon revision and the silicon manufacturer.
Registers 0x04 thru 0x07 are used in the autonegotiation process. They in-
clude the autonegotiation advertisement, autonegotiation link partner ability,
autonegotiation expansion, and autonegotiation next page registers (AN_adv,
AN_lpa, AN_exp respectively).
In the vendor-specific area, Texas Instruments has implemented a TLPHY_id
register. This register is used to identify ThunderLAN-specific PHY devices.
ThunderLAN also implements a specific control register, TLPHY_ctl, and sta-
tus register, TLPHY_sts. The particulars of these registers change from PHY
to PHY. Please refer to Appendix A for the PHY that you are using.
Writing to a register in a PHY through the management interface involves writ-
ing data and clock bits into NetSio
, an internal register, which uses the pointer
host registers. The data unit to or from a PHY register is always 16 bits.
The NetSio register uses three bits to drive the MDIO/MDCLK MII manage-
ment interface. These bits are MCLK, MTXEN, and MDATA. These bits directly
control the voltages present in the management interface and function like
this:
-
MCLK directly controls the MDCLK signal. Setting MCLK in NetSio high
causes a logic 1 to appear on the MDCLK pin. Setting MCLK in the NetSio
register low causes a logic 0 to appear on the MDCLK pin.
-
MTXEN controls the direction of the MDIO pin.
J
When MTXEN is high, MDIO is driven with the value written on
MDATA.
J
When MTXEN is low, MDATA mirrors the MDIO line.
Multiple PHYs can be attached to one MII. PHYs are selected through an ad-
dress which can be in a range from 0x00 to 0x1F. Some vendors’ PHYs have
pins that can be pulled up or down to indicate the PHY address. In order for
a particular PHY to be addressed, the driver must know the PHY address be-
forehand.
ThunderLAN’s internal PHY for 10Base-T can only support two addresses.
When used in conjunction with the rest of the ThunderLAN device, the address
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