DP83620 datasheet(36/105 Pages) TI

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DP83620

SNLS339C – JANUARY 2011 – REVISED APRIL 2013

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Table 5-3. LED Mode Selection

Mode

LED_CFG[1]

LED_CFG[0]

LED_LINK

LED_SPEED

LED_ACT

ON for Good Link

ON in 100 Mb/s

ON for Activity

don't care

OFF for No Link

OFF in 10 Mb/s

OFF for No Activity

ON for Good Link

ON in 100 Mb/s

ON for Collision

BLINK for Activity

OFF in 10 Mb/s

OFF for No Collision

ON for Good Link

ON in 100 Mb/s

ON for Full Duplex

BLINK for Activity

OFF in 10 Mb/s

OFF for Half Duplex

The LED_LINK pin in Mode 1 indicates the link status of the port. In 100BASE-TX mode, link is

established as a result of input receive amplitude compliant with the TP-PMD specifications which will

result in internal generation of signal detect. A 10 Mb/s Link is established as a result of the reception of at

least seven consecutive normal Link Pulses or the reception of a valid 10BASE-T packet. This will cause

the assertion of LED_LINK. LED_LINK will deassert in accordance with the Link Loss Timer as specified

in the IEEE 802.3 specification. In 100BASE-TX mode, an optional fast link loss detection may be enabled

by setting the SD_TIME control in the SD_CNFG register. Enabling fast link loss detection will result in the

LED_LINK deassertion within approximately 1.3 µs of loss of signal on the wire.

The LED_LINK pin in Mode 1 will be OFF when no LINK is present.

The LED_LINK pin in Mode 2 and Mode 3 will be ON to indicate Link is good and BLINK to indicate

activity is present on activity. The BLINK frequency is defined in BLINK_FREQ, bits [7:6] of register

LEDCR (18h).

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/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.

5.6.1

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.

Configuration

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