V62SLASH12615-01XE-R datasheet(34/98 Pages) TI1

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DP83848-EP

SLLSEC6E – SEPTEMBER 2012 – REVISED JUNE 2019

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Detailed Description

The Basic Mode Control Register (BMCR) at address 00h provides control for enabling, disabling, and

restarting the Auto-Negotiation process. When Auto-Negotiation is disabled, the Speed Selection bit in the

BMCR controls switching between 10-Mbps or 100-Mbps operation, and the Duplex Mode bit controls

switching between full duplex operation and half duplex operation. The Speed Selection and Duplex Mode

bits have no effect on the mode of operation when the Auto-Negotiation Enable bit is set.

The Link Speed can be examined through the PHY Status Register (PHYSTS) at address 10h after a Link

is achieved.

The Basic Mode Status Register (BMSR) indicates the set of available abilities for technology types, Auto-

Negotiation ability, and Extended Register Capability. These bits are permanently set to indicate the full

functionality of the DP83848-EP (only the 100BASE-T4 bit is not set because the DP83848-EP does not

support that function).

The BMSR also provides status on:

•

Whether or not Auto-Negotiation is complete

•

Whether or not the Link Partner is advertising that a remote fault has occurred

•

Whether or not valid link has been established

•

Support for Management Frame Preamble suppression

The Auto-Negotiation Advertisement Register (ANAR) indicates the Auto-Negotiation abilities to be

advertised by the DP83848-EP. All available abilities are transmitted by default, but any ability can be

suppressed by writing to the ANAR. Updating the ANAR to suppress an ability is one way for a

management agent to change (restrict) the technology that is used.

The Auto-Negotiation Link Partner Ability Register (ANLPAR) at address 0x05h is used to receive the

base link code word as well as all next page code words during the negotiation. Furthermore, the ANLPAR

will be updated to either 0081h or 0021h for parallel detection to either 100 Mbps or 10 Mbps,

respectively.

The Auto-Negotiation Expansion Register (ANER) indicates additional Auto-Negotiation status. The ANER

provides status on:

•

Whether or not a Parallel Detect Fault has occurred

•

Whether or not the Link Partner supports the Next Page function

•

Whether or not the DP83848-EP supports the Next Page function

•

Whether or not the current page being exchanged by Auto-Negotiation has been received

•

Whether or not the Link Partner supports Auto-Negotiation

5.3.1.3

Auto-Negotiation Parallel Detection

The DP83848-EP supports the Parallel Detection function as defined in the IEEE 802.3u specification.

Parallel Detection requires both the 10 Mbps and 100 Mbps receivers to monitor the receive signal and

report link status to the Auto-Negotiation function. Auto-Negotiation uses this information to configure the

correct technology in the event that the Link Partner does not support Auto-Negotiation but is transmitting

link signals that the 100BASE-TX or 10BASE-T PMAs recognize as valid link signals.

If the DP83848-EP completes Auto-Negotiation as a result of Parallel Detection, bits 5 and 7 within the

ANLPAR register will be set to reflect the mode of operation present in the Link Partner. Note that bits 4:0

of the ANLPAR will also be set to 00001 based on a successful parallel detection to indicate a valid 802.3

selector field. Software may determine that negotiation completed via Parallel Detection by reading a zero

in the Link Partner Auto-Negotiation Able bit once the Auto-Negotiation Complete bit is set. If configured

for parallel detect mode and any condition other than a single good link occurs then the parallel detect

fault bit will be set.

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