AM623: Schematic diagram check for direct connection of RMII interfaces of two MCUs

Hello Rain Wang

I am not sure how you could interface a MAC to MAC. Does the MCU have a MAC or ethernet PHY + Mac

The TX on the MAC is RX on the PHY. Not sure if this is the same on the 2 X MACs connected together.

Let me check internally. You might want to check the same with the MCU provider.

Regards,

Sreenivasa

Hello Rain Wang

Please refer below sections for details on the CPSW3G

12.3.1 Gigabit Ethernet Switch (CPSW3G)

Refer below section for the recommended connection i

Figure 12-426. RMII Interface Typical Application (External Clock Source)

Please check with the MCU vendor for compatibility and the RMII configuration support.

Refer below thread for a general interface overview

(+) TDA4VM: The Driver Development for RMII Connection between Main cpsw9g port1 and MCU cpsw2g port1 (RMII for MAC to MAC) - Processors forum - Processors - TI E2E support forums

Regards,

Sreenivasa

Part Number: AM623

Hi TI team,

                   we send a question before,link:https://e2e.ti.com/support/processors-group/processors/f/processors-forum/1185988/am623-schematic-diagram-check-for-direct-connection-of-rmii-interfaces-of-two-mcus?tisearch=e2e-sitesearch&keymatch=%252525252520user%25252525253A501194#

                   There are still some issues in HW connection blow:

                    1.The HW connection method quoted in the TI reply is shown in the following figure, and TX_ EN and CRS_ DV cross connection, but how do I connect the MDC and MDIO matched with the standard RMII interface between the two MAC devices? Is it direct floating?

                 2.It seems that PHY's RX_ER is not needed when two MAC devices are connected, so how to connect the RX_ER on the MAC device?Is it directly grounded?

I have taken the followup question from ?? ?, and joined it to the original question from Rain.

-Nick

Hi  Nick

       The above is a direct reply from my customer. Please help and support. Thank you

Hello Rain Wang

      2.It seems that PHY's RX_ER is not needed when two MAC devices are connected, so how to connect the RX_ER on the MAC device?Is it directly grounded?

If no trace is connected to the PAD, internal termination can be used.

If there is a trace connected, an external parallel termination is recommended.

Regards,

Sreenivasa

Hello Rain Wang

Regarding the MAC-to-MAC interface 

I am not sure if the MAC-to-MAC interface use case was considered by the design team nor ever tested by silicon validation or application teams. The above link i shared is to indicate or guide you to a working configuration with TI devices.

Not Sure on the need for the MDIO interface for MAC-to-MAC interface.

The MDIO interface consists of two pins, a bidirectional MDIO pin and a Management Data Clock (MDC) pin. All data is transferred synchronously to the MDC which is usually provided by a master controller and sourced to all slave devices.