Datasheet

VCC

165:

2.2 k

165:165:

GND

AN0 = 1AN1 = 1AN_EN = 0

LED_LINK

LED_SPEED

LED

ACT

DP83640

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SNOSAY8E –SEPTEMBER 2007–REVISED APRIL 2013

The LED_SPEED/FX_SD pin indicates 10 or 100 Mb/s data rate of the port. The standard CMOS driver

goes high when operating in 100 Mb/s operation. The functionality of this LED is independent of mode

selected.

The LED_ACT 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 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. 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

5.5.2 LED Direct Control

The DP83640 provides another option to directly control any or all LED outputs through the LED Direct

Control Register (LEDCR), address 18h. The register does not provide read access to LEDs.

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