Specifications

DP83848C , DP83848I
DP83848VYB, DP83848YB
www.ti.com SNLS266E –MAY 2007–REVISED MARCH 2015
6.3.1.2 Auto-Negotiation Register Control
When Auto-Negotiation is enabled, the DP83848VYB transmits the abilities programmed into the Auto-
Negotiation Advertisement register (ANAR) at address 04h through FLP Bursts. Any combination of 10
Mb/s, 100 Mb/s, Half-Duplex, and Full Duplex modes may be selected.
Auto-Negotiation Priority Resolution:
1. 100BASE-TX Full Duplex (Highest Priority)
2. 100BASE-TX Half Duplex
3. 10BASE-T Full Duplex
4. 10BASE-T Half Duplex (Lowest Priority)
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 Mb/s or 100 Mb/s 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 DP83848VYB (only the 100BASE-T4 bit is not set since the DP83848VYB 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 DP83848VYB. 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 Mb/s or 10 Mb/s 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 DP83848VYB 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
6.3.1.3 Auto-Negotiation Parallel Detection
The DP83848VYB supports the Parallel Detection function as defined in the IEEE 802.3 specification.
Parallel Detection requires both the 10 Mb/s and 100 Mb/s 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.
Copyright © 2007–2015, Texas Instruments Incorporated Detailed Description 29
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