DP83848JSQ datasheet(16/80 Pages) TI

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2.0 Configuration

This section includes information on the various configura-

tion options available with the DP83848J. The configura-

tion options described below include:

— Auto-Negotiation

— PHY Address and LED

— Half Duplex vs. Full Duplex

— Isolate mode

— Loopback mode

—BIST

2.1 AUTO-NEGOTIATION

The Auto-Negotiation function provides a mechanism for

exchanging configuration information between two ends of

a link segment and automatically selecting the highest per-

formance mode of operation supported by both devices.

Fast Link Pulse (FLP) Bursts provide the signalling used to

communicate Auto-Negotiation abilities between two

devices at each end of a link segment. For further detail

regarding Auto-Negotiation, refer to Clause 28 of the IEEE

802.3u specification. The DP83848J supports four different

Ethernet protocols (10 Mb/s Half Duplex, 10 Mb/s Full

Duplex, 100 Mb/s Half Duplex, and 100 Mb/s Full Duplex),

so the inclusion of Auto-Negotiation ensures that the high-

est performance protocol will be selected based on the

advertised ability of the Link Partner. In DP83848J, the

Auto-Negotiation function can be controlled either by inter-

nal register access or by the use of AN0 and AN1 pins.

2.1.1 Auto-Negotiation Pin Control

The state of AN0 and AN1 pins determine the specific

mode advertised by the device as given in Table 1.. The

state of AN0 and AN1 pins, upon power-up/reset, deter-

mines the state of bits [8:5] of the ANAR register.

The Auto-Negotiation function selected at power-up or

reset can be changed at any time by writing to the Basic

Mode Control Register (BMCR) at address 0x00h

2.1.2 Auto-Negotiation Register Control

When Auto-Negotiation is enabled, the DP83848J trans-

mits the abilities programmed into the Auto-Negotiation

Advertisement register (ANAR) at address 04h via 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 dis-

abled, 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 oper-

ation when the Auto-Negotiation Enable bit is set.

The Link Speed can be examined through the PHY Status

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

DP83848J (only the 100BASE-T4 bit is not set since the

DP83848J does not support that function).

The BMSR also provides status on:

— Completion of Auto-Negotiation

— Occurrence of a remote fault as advertised by the Link

Partner

— Establishment of a valid link

— Support for Management Frame Preamble suppression

The Auto-Negotiation Advertisement Register (ANAR)

indicates the Auto-Negotiation abilities to be advertised by

the DP83848J. 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 tech-

nology that is used.

The Auto-Negotiation Link Partner Ability Register

(ANLPAR) at address 05h 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) indi-

cates additional Auto-Negotiation status. The ANER pro-

vides status on:

— Occurrence of a Parallel Detect Fault

— Next Page function support by the Link Partner

— Next page support function by DP83848J

— Reception of the current page that is exchanged by Auto-

Negotiation

— Auto-Negotiation support by the Link Partner

Table 1. Auto-Negotiation Modes in DP83848J

AN1

AN0

Advertised Mode

10BASE-T, Half/Full-Duplex

100BASE-TX, Half/Full-Duplex

10BASE-T, Half-Duplex

100BASE-TX, Half-Duplex

10BASE-T, Half/Full-Duplex

100BASE-TX, Half/Full-Duplex

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