DP83849CVSSLASHNOPB datasheet(12/100 Pages) TI2

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1.3 Clock Interface

1.4 LED Interface

The DP83849C supports three configurable LED pins. The

LEDs support two operational modes which are selected

by the LED mode strap and a third operational mode which

is register configurable. The definitions for the LEDs for

each mode are detailed below. Since the LEDs are also

used as strap options, the polarity of the LED output is

dependent on whether the pin is pulled up or down.

Signal Name

Type

Pin #

Description

CRYSTAL/OSCILLATOR INPUT: This pin is the primary clock

reference input for the DP83849C and must be connected to a 25

MHz 0.005% (+50 ppm) clock source. The DP83849C supports

either an external crystal resonator connected across pins X1 and

X2, or an external CMOS-level oscillator source connected to pin

X1 only.

RMII REFERENCE CLOCK: This pin is the primary clock refer-

ence input for the RMII mode and must be connected to a 50 MHz

0.005% (+50 ppm) CMOS-level oscillator source.

CRYSTAL OUTPUT: This pin is the primary clock reference out-

put to connect to an external 25 MHz crystal resonator device.

This pin must be left unconnected if an external CMOS oscillator

clock source is used.

CLK2MAC

CLOCK TO MAC:

In MII mode, this pin provides a 25 MHz clock output to the sys-

tem.

In RMII mode, this pin provides a 50 MHz clock output to the sys-

tem.

This allows other devices to use the reference clock from the

DP83849C without requiring additional clock sources.

If the system does not require the CLK2MAC signal, the

CLK2MAC output should be disabled via the CLK2MAC disable

strap.

Signal Name

Type

Pin #

Description

LED_LINK_A

LED_LINK_B

I/O

LINK LED: In Mode 1, this pin indicates the status of the LINK.

The LED will be ON when Link is good.

LINK/ACT LED: In Mode 2 and Mode 3, this pin indicates transmit

and receive activity in addition to the status of the Link. The LED

will be ON when Link is good. It will blink when the transmitter or

receiver is active.

LED_SPEED_A

LED_SPEED_B

I/O

SPEED LED: The LED is ON when device is in 100 Mb/s and OFF

when in 10 Mb/s. Functionality of this LED is independent of mode

selected.

LED_ACT/LED_COL_A

LED_ACT/LED_COL_B

I/O

ACTIVITY LED: In Mode 1, this pin is the Activity LED which is

ON when activity is present on either Transmit or Receive.

COLLISION/DUPLEX LED: In Mode 2, this pin by default indi-

cates Collision detection. For Mode 3, this LED output may be

programmed to indicate Full-duplex status instead of Collision.

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