TX2 Ethernet - LOM-LED mode ?


I have a question regarding TX2 Ethernet LED.

My question:

TX2 Ethernet LED is LOM-LED mode ?

According to the BCM54610 or BCM89610 datasheet, LED will be LOM-LED mode if LED4 is high on reset.

Fromt page 33 of TX2 OEM Product Design Guide, DMIC4_DAT is pull-up and DMIC4_DAT is LED4.


Yes, it’s pulled up on pin DMIC4_CLK which indicates the LOM-LED mode.

Yes, it’s pulled up on pin DMIC4_CLK which indicates the LOM-LED mode

Then it means that we cannot implement ethernet activity in TX2 DevKit because it woks as
LOM-LED mode ?

In LOM-LED mode, LED1 and LED2 output are fixed like followings according to BCM54610 or BCM89610 datasheet

Table 26: 48-Pin MLP LOM-LED Link Signal Rate Reporting
LED2 Output     LED1 Output       Link Signal Rate
0                      0                       N/A (combination will never occur)
1                      0                       1G link
0                      1                      100M link
1                      1                      10BASE-T link or no link
Note: 0 means LED is turned on. When the BCM89610 operates at LOM-LED mode, the LOM-LED expects that
LED1/LED2 are always connected in the specific configuration on the board, like back-to-back connected LEDs.
This means LED1 and LED2 are always active-low and the LED polarity won't be changed, regardless of board
resistor strapping.

The status of DMIC4_CLK is programmable, if set to low during PHY chip power on reset, it will enter RGMII mode.

[EDIT] LOM-LED mode is only enabled when register 1CH, shadow value is 01011, so the default pin function of LED4 is not to set LOM-LED mode.

I see.

Everything works according to the datasheet.

Thank you so much.

How did you manage to set the DMIC4_CLK low during power up?

Did you manage to get Ethernet activity on the LED on the TX2-DevKit?