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Original question:

AM2434: Question about AM2434 PCIE

AM2434: questions about RGMII part

Jayden Qiu
Intellectual 1405 points
Part Number: AM2434

Hi Team,

This is FAE Jayden, My customer O-net uses AM2434 in their design. They have some questions about the RGMII part in our EVM. 

O-net currently uses the IOSET2 group of RGMII1, and MDIO also uses the IOSET2 group. And they found that some RX signals in the EVM board have pull-up or pull-down resistors, and the RGMII pull-up and pull-down signals of different groups are different (as shown below) ，please help confirm whether it needs to be pulled up or down? What signals are needed?

Schematics above is in our EVM board. Here also attached the schematic o-net just finished, could you help check the RGMII part? Thanks.

AM2434原理图.pdf

Brs

Jayden

  • 0
    TI__Prodigy 510 points

    Hi Jayden,

    Here strapping resistors are completely related to PHY device that is being used on the board. Configuration of the device may be done through the 4-level strap pins or through the management register interface. A pullup resistor and a pulldown resistor of suggested values may be used to set the voltage ratio of the 4-level strap pin input and the supply to select one of the possible selected modes. RX_D0 and RX_D2 are for selecting the address of the PHY device.

    In AM243-EVM Schematic, PHY1 address is 0000 because RX_D0 and RX_D2 both are operating in strap mode "1" therefore both pins are open.
    For PHY2, the address is 0011 RX_D2 is open (strap mode 1) and RX_D0 is pulled up (strap mode 4) with a resistor 2.49kohm.

    Coming to RCX_CTRL, Strap modes 1 and 2 are not applicable for RX_CTRL. The RX_CTRL strap must be configured for strap mode 3 or strap mode 4. Customer can use both the resistors (mode-3) or can use one resistor 2.49kohm(Mode-4). Plese refer to the Datasheet of the respective PHY device on the board for more clarification. Refer this document about strapping pin Configuring Ethernet Devices With 4-Level Straps (Rev. A). (ti.com)

    Thanks and Regards,

    Narayanarao Puli.