Datasheet

VCC

165:

2.2 k:

165:165:

GND

AN0_A = 1AN1_A = 1AN_EN_A = 0

LED_

LINK

LED_SPEED_

LED

_ACT/LED_COL_A

DP83849IF

SNOSAX8D –JUNE 2009–REVISED APRIL 2013

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Activity is defined as configured in LEDACT_RX, bit 8 of register LEDCR (18h). If LEDACT_RX is 0,

Activity is signaled for either transmit or receive. If LEDACT_RX is 1, Activity is only signaled for receive.

The LED_SPEED pin indicates 10 or 100 Mb/s data rate of the port. The LED is ON when operating in

100Mb/s mode and OFF when operating in 10Mb/s mode. The functionality of this LED is independent of

mode selected.

The LED_ACT/LED_COL pin in Mode 1 indicates the presence of either transmit or receive activity. The

LED will be ON for Activity and OFF for No Activity. In Mode 2, this pin indicates the Collision status of the

port. The LED will be ON for Collision and OFF for No Collision.

The LED_ACT/LED_COL pin in Mode 3 indicates Duplex status for 10 Mb/s or 100 Mb/s operation. The

LED will be ON for Full Duplex and OFF for Half Duplex.

In 10 Mb/s half duplex mode, the collision LED is based on the COL signal.

Since these LED pins are also used as strap options, the polarity of the LED is dependent on whether the

pin is pulled up or down.

5.5.1 LEDs

Since the Auto-Negotiation (AN) strap options share the LED output pins, the external components

required for strapping and LED usage must be considered in order to avoid contention.

Specifically, when the LED outputs are used to drive LEDs directly, the active state of each output driver is

dependent on the logic level sampled by the corresponding AN input upon power-up/reset. For example, if

a given AN input is resistively pulled low then the corresponding output will be configured as an active

high driver. Conversely, if a given AN input is resistively pulled high, then the corresponding output will be

configured as an active low driver.

Refer to Figure 5-2 for an example of AN connections to external components at port A. In this example,

the AN strapping results in Auto-Negotiation disabled with 100 Full-Duplex forced.

The adaptive nature of the LED outputs helps to simplify potential implementation issues of these dual

purpose pins.

Figure 5-2. AN Strapping and LED Loading Example

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