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DP83848I: Active LED doesn't work

SUNGMIN PI
Prodigy 90 points
Part Number: DP83848I

Tool/software:

The LED_ACT/COL of the DP83848 is not functioning.
It remains in a HIGH state continuously.
Other LEDs are working properly.

Case 1) When reading PHYCR (0x19, 0d25), the value is 0b1100010111100001.

bit6 (LED_CNFG[1]) = 1, bit5 (LED_CNFG[0]) = 1
LED ACT does not operate


Case 2) After changing LED_CNFG[1] = 0 and LED_CNFG[0] = 0,

The value becomes 0b1100010110000001
LED ACT still does not operate

The circuit is used in RMII mode, and the register values appear as shown in each case.


Please let me know the reason.
I am attaching the circuit diagram.

Thank you for your help.

  • +1
    TI__Genius 12461 points

    Hi Sungmin,

    Just to make sure, does the LED_LINK blink on mode 2 for activity? On mode 2, LED_LINK is supposed to blink to indicate activity is present on activity with the same test setup to test LED_ACT on mode 1?

    SUNGMIN PI said:

    Case 2) After changing LED_CNFG[1] = 0 and LED_CNFG[0] = 0,

    The value becomes 0b1100010110000001
    LED ACT still does not operate

    Note that in this case LED ACT will only be ON if there is a collision. Have you tried causing a collision to see if the LED turns on?

    Based on the information you gave us, I would suggest trying mode 3 which would detect the duplex status of the operation to see if the LED is not ON when the PHY is on full duplex. 

    Could we also get a pdf version of the schematic? The screenshot is very pixelated and hard to read. 

    Please let me know. 
    Best, 
    J