Datasheet

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4.0 Register Set (Continued)
DP83815
4.3 Internal PHY Registers
The Internal Phy Registers are only 16 bits wide. Bits [31:16] are not used. In the following register definitions under the
‘Default’ heading, the following definitions hold true:
—RW=Read Write access
—RO=Read Only access
— LL=Latched Low and held until read, based upon the occurrence of the corresponding event
—LH=Latched High and held until read, based upon the occurrence of the corresponding event
— SC=Register sets on event occurrence and Self-Clears when event ends
— P=Register bit is Permanently set to a default value
—COR=Clear On Read
4.3.1 Basic Mode Control Register
Tag: BMCR Size: 16 bits Hard Reset: XX00h
Offset: 0080h Access: Read Write
Bit Bit Name Description
15 Reset Reset: Default: 0, RW/SC
1 = Initiate software Reset / Reset in Process
0 = Normal operation
This bit, which is self-clearing, returns a value of one until the reset process is complete. The configuration
is re-strapped.
14 Loopback Loopback: Default: 0
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 de-scrambler to lose synchronization and produce a 500 µs “dead time”
before any valid data will appear at the MII receive outputs.
13 Speed
Selection
Speed Select: Default: dependent on the setting of the ANEG_SEL bits in the CFG register
When auto-negotiation is disabled writing to this bit allows the port speed to be selected.
1 = 100 Mb/s
0 = 10 Mb/s
12 Auto-
Negotiation
Enable
Auto-Negotiation Enable: Default: dependent on the setting of the ANEG_SEL bits in the CFG register
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 port speed and duplex mode.
11 Power Down Power Down: Default: 0
1 = Power down
0 = Normal operation
Setting this bit powers down the port.
10 Isolate Isolate: Default: 0
1 = Isolates the port from the MII with the exception of the serial management.
0 = Normal operation
9 Restart Auto-
Negotiation
Restart Auto-Negotiation: Default: 0, RW/SC
1 = Restart Auto-Negotiation
0 = Normal operation
When this bit is set, it re-initiates the Auto-Negotiation process. If Auto-Negotiation is disabled (bit 12 =
0), this bit is ignored. This bit is self-clearing and will remain a value of 1 until Auto-Negotiation is initiated,
whereupon it will self-clear. Operation of the Auto-Negotiation process is not affected by the management
entity clearing this bit.
8 Duplex Mode Duplex Mode: Default: dependent on the setting of the ANEG_SEL bits in the CFG register
When auto-negotiation is disabled writing to this bit allows the port Duplex capability to be selected.
1 = Full Duplex operation
0 = Half Duplex operation
Obsolete