DM9161B
10/100 Mbps Fast Ethernet Physical Layer Single Chip Transceiver
23 Final
Version: DM9161B-12-DS-F01
January 31, 2008
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
When 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
auto-negotiation selected medium 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
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 DM9161B from the MII with the exception of the serial
management. (When this bit is asserted, the DM9161B 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 to a value of 1 until
auto-negotiation is initiated by the DM9161B. The operation of the
auto-negotiation process will not be affected by the management
entity that clears this bit
0 = Normal operation
