Specifications

DP83848C , DP83848I
DP83848VYB, DP83848YB
www.ti.com SNLS266E –MAY 2007–REVISED MARCH 2015
Table 6-2. LED Mode Selection
LED_CFG[1] (bit LED_CFG[0] (bit 5)
Mode LED_LINK LED_SPEED LED_ACT/LED_COL
6) or (pin 40)
ON for Good Link ON in 100 Mb/s ON for Activity
1 don't care 1
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
2 0 0
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
3 1 0
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-T 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.
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 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 10 Mb/s mode. The functionality of this LED is independent of
mode selected.
The LED_ACT/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/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.
6.3.3.1 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 6-1 for an example of AN connections to external components. In this example, the AN
strapping results in Auto-Negotiation disabled with 10/100 Half/Full-Duplex advertised .
The adaptive nature of the LED outputs helps to simplify potential implementation issues of these dual
purpose pins.
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