LXT975B datasheet(38/74 Pages) INTEL

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LXT974/LXT975 — Fast Ethernet 10/100 Quad Transceivers

Datasheet

2.7.1

Serial LED Output

The LXT974/975 provides a serial LED interface which should be attached to an external shift

conditions:

• Transmit (T)

0 = Transmit active

1 = Transmit inactive

• Receive (R)

0 = Receive active

1 = Receive inactive

• Link (L)

0 = Link active

1 = Link inactive

• Duplex (D)

0 = Half-Duplex

1 = Full-Duplex

• Speed (S)

0 = 100 Mbps

1 = 10 Mbps

• Collision (C)

0 = Collision active

1 = Collision inactive

LED Data is output on LEDDAT in sets of 24 bits. The serial burst is repeated every 1 ms. A

status change in any bit also triggers an immediate serial burst (following the minimum inter-burst

gap of 10

µs). LEDENA is driven High for the duration of the LEDDAT output.

2.7.2

Per Port LEDs

The LXT974/975 provides three LED outputs for each port (LEDn_0, LEDn_1 and LEDn_2,

where n = port number). These outputs can directly drive LEDs to indicate activity and collision

status. The active Low “on” times are normally extended for improved LED visibility. The on-

time extension can be disabled by setting bit 16.0 = 1.

2.7.2.1

LEDn_0

In default mode, LED_0 indicates transmitter active. However, LEDn_0 is programmable and may

also be set to indicate receiver active, link, or full-duplex status. Refer to LED Configuration

2.7.2.2

LEDn_1

In default mode, LED_1 indicates receiver active. However, LEDn_1 is programmable and may

also be set to indicate link status, full-duplex status or operating speed. Refer to LED

Configuration Register, Table 51 on page 68, for details on programming options.

2.7.2.3

LEDn_2

In default mode, active Low output indicates link up. However, LEDn_2 is programmable and

may also be set to indicate full-duplex status, operating speed or collision. Refer to LED

Configuration Register, Table 51 on page 68, for details on programming options.

LXT975B Datasheet(PDF) 38 Page - Intel Corporation

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