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DP83867E: Recommended design

na na78
Guru 16770 points
Part Number: DP83867E


Hi

I have questions of DP83867E.

1. Power supply
We can see the description of POWER pins like "Each pin requires a 1uF and 0.1uF capacitor to GND" in Pin Functions of Datasheet.
If these capacitor is not offered at each supply pins, what impact can be considered?
For example, the following capacitors and connection can be acceptable?

2. JTAG port
We would leave JTAG port open because it is not in use.
What is the purpose of JTAG port?

Can user access the register of DP83867E by JTAG interface?

3. EVM setting
In DP83867E EVM, RX_CTRL doesn't have external strap resistor (open) and it means RX_CTRL is MODE 1 according to datasheet.
However, RX_CTRL of MODE 1 is not available. How does EVM work in this case?

BestRegards

BestRegards

  • 0
    TI__Mastermind 18425 points
    Hello,

    The decoupling capacitor requirement mentioned in the datasheet is derived from our validation process. Reducing decoupling on power supply is not recommended. If there is noise on the supply, systems with reduced decoupling may see link instabilities or data errors

    JTAG is used for boundary scan. DP83867 registers cannot be accessed via the JTAG port. We recommend terminating the JTAG port when not being used but this is not a requirement. Please refer to the Unused pins section in the datasheet for more information on terminating unused pins.

    RX_CTRL strap conditions were updated after the release of EVM. We will update the EVM to change RX_CTRL strap to mode 3. If you have the EVM now, you can update the strap resistor to put RX_CTRL in mode 3. Other option is to write '0' to bit 7 in register 0x31 via register access. Please note that RX_CTRL mode 1 & 2 may cause the EVM to have link instability in some cases. This will not stop the EVM from working completely.

    -Regards,
    Aniruddha