LXT970ATC datasheet(29/74 Pages) INTEL

29 / 74 page

Dual-Speed Fast Ethernet Transceiver — LXT970A

Datasheet

2.3.3

Bias Circuit Requirements

A 22.1 k

Ω 1% resistor must be tied between the RBIAS input and ground. High-speed signals

should be kept away from this resistor. Follow the layout recommendations given in the Design

Recommendations section on page 42.

2.4

Initialization

At power-up or reset, the LXT970A performs the initialization sequence shown in Figure 11.

2.4.1

Control Mode Selection

Mode control selection is provided via the MDDIS pin as shown in Table 15. When pin 15

(MDDIS) is High, the LXT970A enters Manual Control Mode. When MDDIS is Low, MDIO

Control Mode is enabled.

2.4.1.1

MDIO Control Mode

In the MDIO Control mode, the LXT970A reads the Hardware Control Interface pins to set the

initial (default) values of the MDIO registers. Once the initial values are set, bit control reverts to

the MDIO interface.

2.4.1.2

Manual Control Mode

In the Manual Control Mode, LXT970A disables direct write operations to the MDIO registers via

the MDIO Interface. The LXT970A continuously monitors the Hardware Control Interface pins

and updates the MDIO registers accordingly.

2.4.2

Link Configuration

When the LXT970A is first powered on, reset, or encounters a link failure state, it must determine

the line speed and operating conditions to use for the network link. The LXT970A first checks the

MDIO registers (initialized via the Hardware Control Interface or MDIO Interface) for operating

instructions. Both control modes allow the user to either force the LXT970A to a specific

configuration or allow it to auto-negotiate the optimum configuration with its link partner.

Table 15. Mode Control Settings

Mode

MDDIS

RESET

PWRDWN

MDIO Control

Low

High

Low

Manual Control

High

Low

Reset

Low

Power Down

High

LXT970ATC датащи(PDF) 29 Page - Intel Corporation

LXT970ATC датащи(HTML) 29 Page - Intel Corporation

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74

датащи скачать

ссылки URL