AM335x RMII Ethernet connection without RX_ER

takeshi matsuzaki

Expert 2030 points

Hello,

My customer is planning to use Eterhnet Switching HUB IC with RMII I/F to AM335x.
But that Switching HUB IC doesn't have RMII_RXER signal out.
I leaned RX_ER is optional in RMII.
http://e2e.ti.com/support/arm/sitara_arm/f/791/t/214462.aspx

So, could he connect that HUB IC to AM335x ?

Regards,
Takeshi Matsuzaki

over 9 years ago

0 Biser Gatchev-XID over 9 years ago

TI__Guru**** 393215 points

Hi Matsuzaki-san,

Please note that MAC-to-MAC connection has not been verified on the AM335X, although there is information that some customers have used it successfully. The proven path to go is if the external switch IC supports PHY mode on the MAC interface to AM335X.

RX_ER is optional on the RMII interface.

0 takeshi matsuzaki over 9 years ago in reply to Biser Gatchev-XID

Expert 2030 points

Biser-san,

Thank you for reply.
I understood I need to check if the the external switch IC supports PHY mode.
Supposing that the switch IC supports PHY mode and my customer desided to use it,
where the RMII_RXER of AM335x should be connected to ? VSS ?

Regards,
Takeshi Matsuzaki

0 Biser Gatchev-XID over 9 years ago in reply to takeshi matsuzaki

TI__Guru**** 393215 points

You can leave it open and use internal pullup/pulldown as needed.

0 takeshi matsuzaki over 9 years ago in reply to Biser Gatchev-XID

Expert 2030 points

Thank you Biser, I got it.

Regards,
Takeshi Matsuzaki

0 peaves over 9 years ago in reply to takeshi matsuzaki

TI__Guru 55425 points

The rmii1_rxer and rmii2_rxer inputs are active high, so they should remain low for normal operation.

These inputs will be driven low internally when the respective pin mux mode if configured for any other mode. Inside the AM335x device, the CPSW module will always see a low applied to its RXER input if you do not configure the pin mux register for the MII_RX_ER terminal to mode 1 or the pin mux register for the GPMC_WPn terminal to mode 3.

The MII_RX_ER terminal should be pulled low externally if its pin mux register is set to mode 1 and not sourced by an RMII PHY.

The GPMC_WPn terminal should be pulled low externally if its pin mux register is set to mode 3 and not sourced by an RMII PHY.

Regards,
Paul

0 takeshi matsuzaki over 9 years ago in reply to peaves

Expert 2030 points

Good details, thank you Paul.

I understood I need external PullDown.

Regards,
Takeshi Matsuzaki

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AM335x RMII Ethernet connection without RX_ER