Datasheet

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8.0 Register Block (Continued)
Table 6. Basic Mode Control Register (BMCR) Address 00h
Bit Bit Name Default Description
15 Reset 0, RW/SC Reset:
1 = Initiate software Reset / Reset in Process
0 = Normal operation
This bit sets the status and control registers of the PHY to their
default states. This self-clearing bit returns a value of one until the
reset process is complete (approximately 1.2 ms for reset dura-
tion). Reset is finished once the Auto-Negotiation process has
begun or the device has entered its forced mode.
14 Loopback 0, RW Loopback:
1 = Loopback enabled
0 = Normal operation
The loopback function enables MII transmit data to be routed to
the MII receive data path.
Setting this bit may cause the descrambler to lose synchroniza-
tion and produce a 500 µs “dead time” before any valid data will
appear at the MII receive outputs.
13 Speed Selection Strap, RW Speed Select:
1 = 100 Mb/s
0 = 10 Mb/s
Link speed is selected by this bit or by Auto-Negotiation if bit 12
of this register is set (in which case, the value of this bit is ignored)
At reset, this bit is set according to the strap configuration of the
AN0 and AN1 pins. After reset, this bit may be written to by soft-
ware.
12 Auto-Negotiation En-
able
Strap, RW Auto-Negotiation Enable:
1 = Auto-Negotiation Enabled - bits 8 and 13 of this register are
ignored when this bit is set.
0 = Auto-Negotiation Disabled - bits 8 and 13 determine the link
speed and mode.
At reset, this bit is set according to the strap configuration of the
AN0 and AN1 pins. After reset, this bit may be written to by soft-
ware.
11 Power Down 0, RW Power Down:
1 = Power Down
0 = Normal Operation
Setting this bit configures the PHYTER for minimum power re-
quirements.While in Power Down mode, the PHYTER is not ca-
pable of transmitting or receiving data on an active network.
Additionally, the PHYTER is not capable of "Wake-on-LAN" and
will not react to receive data while in Power Down mode. Power
Down mode is useful for scenarios where minimum system power
is desired (ie. Green PCs) but can only be used in systems that
have control over the PHYTER via Serial MII management.