AM335x EVM's user guide

any idea?

The original plan was to have another RGMII PHY on the EVM daughter card connected to the RGMII2 port.

The high speed signal quality requirements for this interface were not comprehended during PCB layout, so it may be very difficult to get this to work.

Regards,

Paul

Paul,

Thank you for the information.

I understood it may be difficult to add RGMII2 port into the EVM.

Meanwhile we are designing our custom board and we 

would like to have two Giga bit ethernet ports.

As you said designing Giga bit ethernet port would be difficult,

could you please let us know if there is any reference or documents that could be helpful to 

design our custom board.

Regards.

Currently we do not have a reference design that includes a RGMII Ethernet PHY connected to the RGMII2 port.  You can use the RGMII Ethernet PHY to RGMII1 port connections of the EVM as an example for connecting a RGMII Ethernet PHY to the RGMII2 port. 

I recommend the following PCB layout guidelines.  The RGMII PHY should be place near the RJ-45 connector, but not too far away from the AM335x.  It would be best if you could keep the etch length between the RGMII Ethernet PHY and AM335x to be less than 5 inches.  These signals operate at 125MHz double data rate so it is important you provide good impedance control to prevent overshoot/undershoot which could erode timing margin.  The transmit and receive data paths use source synchronous clocking so you should length match the data and control signals to the respective clock signal if the RGMII Ethernet PHY being used supports internal delay mode.  Most RGMII Ethernet PHYs support internal delay mode, but if it does not you may need to skew the clock signal length relative to the data and control signals to meet timing requirements.  Note: AM335x does not support internal delay mode.

Regards,

Paul

Thank you so much Paul,

Your suggestion is very important for our design.

One more final confirmation, we need to test two Ethernet ports on the EVM.

and as you said it may be difficult to add RGMII2 port into the EVM.

Just in case we would like to know if we can add a  100 Base port  instead of  1000 Base.

and my guess is that, 100 Base may not need high speed signal quality requirements.

Regards.

The current General Purpose EVM does not support a second Ethernet PHY due to the pin muxing requirements of other supported functions on the EVM.  The EVM Hardware User's Guide and AM335x datasheet which are available from the AM335x tools page can show you which signals would be required for connecting a second PHY.

Thank you.

Please let me have one final confirmation, 
do you mean to say, it is impossible to connect second external PHY on the EVM?

I believe in this EVM, the MII/RMII multiplexed pins are used for SDIO/WLAN.
So if we don't use or disconnect SDIO/WLAN fuction, we could use it 
for a second ethernet port.

Regards.