i.MX8M Mini Ethernet RGMII at 3.3V

[andreamengalli]

Hi,

I'm working on a new custom carrier board based on NXP 8MMINILPD4-CPU module. Ethernet PHY on the carrier board is TI DP83869HM and it is interfaced in RGMII mode with NVCC_ENET at 3.3V. I'm debugging the system for troubles in Gigabit connection (10Megabit and 100Megabit are Ok). Today I have seen the following message by Gurasambula: he wrote that i.MX8M Mini support RGMII mode only at 1.8V or 2.5V.  On datasheet IMX8MMIEC Rev. 0.2, I see that NVCC_ENET can be 1.8 or 2.5 or 3.3 volts.

Please, can you confirm that RGMII mode at 3.3V is not supported?

[gusarambula]

Hello Andrea Mengalli,

I understand your concern as documentation is not clear on this restriction. I will check internally again and escalate this so it gets mentioned on the documentation if need be. I will let you know as soon as I have more information.

Regards,

[gusarambula]

Hello Andrea Mengalli,

My apologies. I confirmed internally that the Ethernet MAC in i.MX8M Mini can support 2.5V RGMII and 1.8V/3.3V RMII well.

The situation here is that only 2.5V CMOS and 1.5V HSTL RGMII are defined on their standard specification, and no 3.3V RGMII has been defined formally as part of the RGMII standard.

I hope this helps.

Regards,

[mr_e]

Hello @gusarambula  @gusarambula 

Thanks for share that "i.MX8M Mini can support 2.5V RGMII and 1.8V/3.3V RMII well."

And just like i am using AR8031/AR8035 for projects, but the MX8M mini EVK schematic highlight that "Software MUST configure PHY RGMII port for 1.8V operation. "Default = 1.5V"  

Does it mean we have to not only make NNVCC_ENET as 1.8V, but also need to configure AR8031/AR8031 RGMII as 1.8V signal level? and how to do it in detail? 

May i have NXP RD's clear advise and feedback about them. we hope to make i.MX8M Mini Ethernet RGMII at 1.8V as EVK did.

[andreamengalli]

To my regret, I take note of the information and corrective action.
Thanks for your support.