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65
Networking Silicon — GD82559ER
9. PHY Unit Registers
The 82559ER provides status and accepts management information via the Management Data
Interface (MDI) within the CSR space.
Acronyms mentioned in the registers are defined as follows:
9.1 MDI Registers 0 - 7
9.1.1 Register 0: Control Register Bit Definitions
SC - self cleared
RO - read only
E - EEPROM setting affects content
LL - latch low
LH - latch high
Bit(s) Name Description Default R/W
15 Reset This bit sets the status and control register of the PHY to
their default states and is self-clearing. The PHY returns
a value of one until the reset process has completed and
accepts a read or write transaction.
1 = PHY Reset
0RW
SC
14 Loopback This bit enables loopback of transmit data nibbles from
the TXD[3:0] signals to the receive data path. The PHY
unit’s receive circuitry is isolated from the network.
Note that this may cause the descrambler to lose
synchronization and produce 560 nanoseconds of “dead
time.”
Note also that the loopback configuration bit takes priority
over the Loopback MDI bit.
1 = Loopback enabled
0 = Loopback disabled (Normal operation)
0RW
13 Speed Selection This bit controls speed when Auto-Negotiation is disabled
and is valid on read when Auto-Negotiation is disabled.
1 = 100 Mbps
0 = 10 Mbps
1RW
12 Auto-Negotiation
Enable
This bit enables Auto-Negotiation. Bits 13 and 8, Speed
Selection and Duplex Mode, respectively, are ignored
when Auto-Negotiation is enabled.
1 = Auto-Negotiation enabled
0 = Auto-Negotiation disabled
1RW
11 Power-Down This bit sets the PHY unit into a low power mode. In low
power mode, the PHY unit consumes no more than 30
mA.
1 = Power-Down enabled
0 = Power-Down disabled (Normal operation)
0RW
10 Reserved This bit is reserved and should be set to 0b. 0 RW