DM9000
ISA to Ethernet MAC controller with integrated 10/100 PHY
Final
23
Version: DM9000-DS-F01
April 12, 2002
8.1 Basic Mode Control Register (BMCR) - 00
Bit
Bit Name
Default
Description
0.15
Reset
0, RW/SC
Reset
1=Software reset
0=Normal operation
This bit sets the status and controls the PHY registers to their default
states. This bit, which is self-clearing, will keep returning a value of
one until the reset process is completed
0.14
Loopback
0, RW
Loopback
Loop-back control register
1 = Loop-back enabled
0 = Normal operation
In 100Mbps operation mode, setting this bit may cause the
descrambler to lose synchronization and produce a 720ms "dead
time" before any valid data appears at the MII receive outputs
0.13
Speed selection
1, RW
Speed Select
1 = 100Mbps
0 = 10Mbps
Link speed may be selected either by this bit or by auto-negotiation.
When auto-negotiation is enabled and bit 12 is set, this bit will return
to the auto-negotiation selected media type
0.12
Auto-
negotiation
enable
1, RW
Auto-negotiation Enable
1 = Auto-negotiation is enabled, bit 8 and 13 will be in auto-
negotiation status
0.11
Power down
0, RW
Power Down
While in the power-down state, the PHY should respond to the
management transactions. During the transition to power-down state
and while in the power-down state, the PHY should not generate
spurious signals on the MII
1=Power down
0=Normal operation
0.10
Isolate
0,RW
Isolate
1 = Isolates the PHY from the MII with the exception of the serial
management. (When this bit is asserted, the PHY does not respond
to the TXD [0:3], TX_EN, and TX_ER inputs, and it shall present a
high impedance on its TX_CLK, RX_CLK, RX_DV, RX_ER,
RXD[0:3], COL and CRS outputs. When PHY is isolated from the MII
it shall respond to the management transactions)
0 = Normal operation
0.9
Restart auto-
negotiation
0,RW/SC
Restart Auto-negotiation
1 = Restart auto-negotiation. Re-initiates the auto-negotiation
process. When auto-negotiation is disabled (bit 12 of this register
cleared), this bit has no function and it should be cleared. This bit is
self-clearing and it will keep returning a value of 1 until auto-
negotiation is initiated by the PHY. The operation of the auto-
negotiation process will not be affected by the management entity
that clears this bit
0 = Normal operation