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DP83849C Datasheet(PDF) 11 Page - National Semiconductor (TI) |
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DP83849C Datasheet(HTML) 11 Page - National Semiconductor (TI) |
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11 / 98 page  11 www.national.com 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 X1 I 70 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. X2 O 69 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 O 68 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 19 43 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 20 42 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 21 41 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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Similar Description - DP83849C_08 |
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