AR8031-AL1B データシートの表示（PDF） - Unspecified

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AR8031-AL1B

AR8031 Integrated 10/100/1000 Mbps Ethernet Transceiver

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feedback equalizer (DFE) for the best-

optimized signal-to-noise (SNR) ratio.

2.4.7 Auto-Negotiation

The AR8031 device supports 10/100/1000

BASE-T Copper auto-negotiation in accordance

with IEEE 802.3 clauses 28 and 40. Auto-

negotiation provides a mechanism for

transferring information between a pair of link

partners to choose the best possible mode of

operation in terms of speed, duplex modes,

and master/slave preference. Auto-negotiation

is initiated upon any of the following scenarios:

n Power-up reset

n Hardware reset

n Software reset

n Auto-negotiation restart

n Transition from power-down to power-up

n The link goes down

If auto-negotiation is disabled, a 10 BASE-Te or

100 BASE-TX can be manually selected using

the IEEE MII registers.

NOTE: Smartspeed enable bit requires a software

reset to take effect after writing (write register

0x0[15]).

2.4.8 Smartspeed Function

The Atheros Smartspeed function is an

enhanced feature of auto-negotiation that

allows the AR8031 device to fall back in speed

based on cabling conditions as well as operate

over CAT3 cabling (in 10 BASE-T mode) or

two-pair CAT5 cabling (in 100 BASE-TX mode).

By default, the Smartspeed feature is enabled.

Refer to the register “Smart Speed Register” on

page 75, which describes how to set the

parameters. Set these register bits to control the

Smartspeed feature:

n Bit [5]: 1 = Enables Smartspeed (default)

n Bits [4:2]: Sets the number of link attempts

before adjusting

n Bit [1]: Timer to determine the stable link

condition

NOTE: Smartspeed enable bit needs a software

reset (write register 0x0[15] = 1’b1 to take effect

after writing.

2.4.9 Automatic MDI/MDIX Crossover

During auto-negotiation, the AR8031 device

automatically determines and sets the required

MDI configuration, eliminating the need for

external crossover cable. If the remote device

also implements automatic MDI crossover, the

crossover algorithm as described in IEEE 802.3

clause 40.4.4 ensures that only one device

performs the required crossover.

2.4.10 Polarity Correction

If cabling has been incorrectly wired, the

AR8031 automatically corrects polarity errors

on the receive pairs in 1000 BASE-T, 1000BASE-

TX, and 10 BASE-Te modes.

2.5 Loopback Modes

2.5.1 Digital Loopback

Digital loopback provides the ability to loop

transmitted data back to the receiver using

digital circuitry in the AR8031 device. Figure 2-

4 shows a block diagram of digital loopback.

MAC/

Switch

RGMII/

SGMII

PHY

PHY

Digital

AFE

Figure 2-4. Digital Loopback

Followings are the register settings for

loopback mode selection:

n 1000M loopback: register 0x0 = 0x4140

n 100M loopback: register 0x0 = 0x6100

n 10M loopback: register 0x0 = 0x4100

2.5.2 External Cable Loopback

External cable loopback loops RGMII/SGMII

Tx to RGMII/SGMII Rx through a complete

digital and analog path and an external cable,

thus testing all the digital data paths and all the

analog circuits. Figure 2-5 shows a block

diagram of external cable loopback.

MAC/

Switch

RGMII

PHY

PHY

/SGMII

Digital

AFE

Figure 2-5. External Cable Loopback

Atheros Communications, Inc.

COMPANY CONFIDENTIAL

AR8031 Integrated 10/100/1000 Mbps Ethernet Transceiver • 19

August 2011 • 19

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