Figure 20-12. Integrated PHY Diagram
TX
RX
RECEIVE BLOCK
10BASE-T and
100BASE-TX
TRANSMIT BLOCK
10BASE-T and
100BASE-TX
PHY
Registers
Auto-
Negotiation
State Machine
Clock
Generation
DAC
ADC
Auto MDIX
LED Drivers
Cable
Diagnostics
Serial
Management
Interface
EN0MDIO
EN0MDC
EN0TXOP /
EN0TXON
EN0RXIP /
EN0RXIN
EN0LEDn
Extended PHY
Registers
25 MHz MOSC
20.4.2 Functional Description
The following sections describe the functional characteristics of the integrated PHY.
20.4.2.1 Auto-Negotiation
The Ethernet PHY can auto-negotiate to operate in 10Base-T or 100Base-TX. When the Ethernet
PHY is enabled or on the deassertion of software reset, the Ethernet MAC Peripheral Configuration
Register (EMACPC) register, offset 0xFC4, is configured such that auto-negotiation is enabled and
the auto negotiation mode (ANMODE) bit field is programmed to 10Base-T,Half/Full-Duplex
100Base-TX, Half/Full-Duplex. With auto-negotiation enabled, the PHY negotiates with the link
partner to determine the speed and duplex mode with which to operate. If the link partner is unable
to auto-negotiate, the PHY goes into parallel-detect mode to determine the speed of the link partner.
Under parallel-detect mode, the duplex mode is fixed at half-duplex. The PHY supports four different
Ethernet protocols (10Mbs Half-Duplex, 10Mbs Full-Duplex, 100Mbs Half-Duplex, and 100Mbs
Full-Duplex). Auto-Negotiation selects the highest performance protocol based on the advertised
ability of the Link Partner. If a different auto-negotiation configuration is required other than the reset
initialization values, the application can customize the configuration of the ANEN bit and ANMODE bit
field as described in “Custom Configuration” on page 1466. The values of ANEN and ANMODE determine
whether the PHY is forced into a specific mode, or if Auto-negotiation advertises a specific ability
(or abilities) as listed in Table 20-20 on page 1458 and Table 20-21 on page 1459:
Table 20-20. Forced Mode Configurations
Forced ModeANMODEANEN value
10Base-T, Half-Duplex0x00
10Base-T, Full-Duplex0x10
100Base-TX, Half-Duplex0x20
100Base-TX, Full-Duplex0x30
June 18, 20141458
Texas Instruments-Production Data
Ethernet Controller
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